At that instant a fusillade of bullets cut the ground all about them, and the six men suddenly realized that they were under a pitiless and well-directed machine-gun fire.

And through it all they dared not return the fire, could not even utter a word to each other without fear of giving the enemy a closer range upon them.

It was a terrible three minutes for that isolated little group of Americans, for bullets were striking all around them, the nearest not more than ten feet away, and there was every possibility that another detachment might be flanking them, to cut them off later in their retreat, in case the machine-gun did not effectively do its deadly work.

There was but one desperate course open to them, and that Lieutenant Mackinson ordered at the instant the firing ceased.

"Run!" he ordered, in a shrill whisper. "Run straight toward our own lines for about a quarter of a mile and then detour to the south."

And off they started, each with all the speed he had in him. The renewal of the machine-gun fire compelled them to take a zig-zag course, however, and in this way for the first five minutes they all kept together.

Then Tom Rawle, who, with the lieutenant, had been a little in the lead, gradually dropped back until he was abreast of Joe and Jerry, who were running together, and then behind them, reaching Frank Hoskins and Slim, who were bringing up a loudly puffing rear.

Finally, as they began to pass him, too, and his lagging pace became noticeable, he urged them ahead and told them not to mind him.

"I got one of those bullets in the hip," Rawle told them, to the surprise of all, for up to that moment he hadn't uttered a sound. "It cuts down my speed, but it's nothing serious, I guess. You keep right on and I'll follow as rapidly as I can."

"I'm almost winded myself," said Slim. "I'll stick with Tom; you fellows keep right on. We'll join you in a few minutes after you stop. Joe, I'll give that 'whip-poor-will' call if we can't locate you. At any rate, we know our way back to the American lines."

"Not so loud," warned Lieutenant Mackinson, as he slowed down. "I guess you are right," he continued. "You stay along with Rawle, but the two of you try to follow as quickly as possible, so that we can get Tom back to the lines for medical attention. It is necessary that I have the others with me, though, for we must not only accomplish our mission, but also give the commander that intercepted German message."

And so the little group parted, there in the blackness of night "somewhere in France," the lieutenant, Hoskins, Joe and Jerry to forge ahead as rapidly as they could in a detour that would again take them back into the enemy territory, but in another place, while Slim and the wounded Rawle came along at a slower pace.

The latter had been wounded more seriously than he knew, though, and he had not gone more than three hundred yards further before the loss of blood had so weakened him that he had to stop running and hobble along in a painful, limping gait, leaning heavily upon Slim's shoulder.

"Guess I'll have to quit," he said, a little later on. "Can't go much further." And even as he spoke he sank to the ground.

While Tom Rawle assured him that it "wasn't much of a wound," Slim, who was doing the best he could to stop the flow of blood with his handkerchief, knew that it was a bad injury, indeed, unless it was given early attention.

"I'll try to get one of the others to return," he said, "and then we can send to our lines for a stretcher to get you in."

"Nonsense," said Rawle, "I can walk; I'll show you."

But it was a pitiful effort, and unsuccessful, and Tom himself had to admit that he "guessed he was out of business" for a little while.

Thereupon Slim puckered up his lips and imitated the low but far-carrying call of the whip-poor-will—the call that he and Joe and Jerry had used so much to summon each other at Brighton.

He remained silent for a moment listening, but there was no answer except the distant rumble of the heavy artillery fire. He repeated the call several times. Here and there to the north of them occasional rockets went up from either line, but their brief light divulged nothing in the way of encouragement.

"It's not doing you any good to sit here without attention," said Slim at last. "Here is your revolver right alongside you. I will be back within half an hour. I am going to scout around for help."

"But don't take any chances for me," Tom Rawle warned him. "I guess I could crawl back to camp, at that."

"No, you couldn't," Slim declared, "and mind you don't try it. I'll be back for you in a very short time."

He disappeared in the direction that the rest of the party had taken, leaving Rawle there to await his return. Half an hour later he managed to find the spot again, but without the aid he had gone to get. Not a trace of the others had he been able to find.

But that was not the worst of it. Tom Rawle, helpless for all his big body and physical strength, lay stretched out upon the ground unconscious, a pool of blood by his side!

Slim put his water flask to the wounded man's lips and tried to rouse him, but without avail.

"Whip-poor-will-l-l," whistled Slim. "Whip-poor-will-l-l." But the sound was lost somewhere in the denseness of the night, and there was not even an echo for response.

Slim was growing desperate. At any time they might be discovered by an enemy scouting party, and then they would either be bullets' victims or prisoners of war. Yet he knew that he could not hope to carry Tom Rawle back to the American lines. Rawle's dead weight would have been a difficult burden for a man of twice Slim's strength, and he knew it.

What should he do? Unnecessary delay might cost the other man's life. Already his wound had caused him to lose consciousness.

As he turned the thing over in his mind there came faintly, ever so faintly, to him from far, far to the south, as though but a breath of wind, the familiar "Whip-poor-will."

"Whip-poor-will-l-l," shrilled back Slim.

He waited, but there was no answer. It was as though a whip-poor-will itself was mocking his plight.

"Whip-poor-will-l-l," Slim whistled again, and thrice, but each time there was nothing but the grim silence for reply.

"Tom," he whispered into Rawle's ear, gently shaking the wounded man. "Tom, can you get up? I'll help you back. We can make it somehow together."

But here again only the weak breathing of his comrade testified to their plight.

"Better to take the one chance that's left us," muttered Slim to himself, as he pulled Rawle's revolver from under him, to make sure that it was fully loaded. "Yes," he continued, "it's better to risk discovery than this fellow's life."

He took his own automatic from its holster and carefully examined it also.

Then, with a revolver in either hand, pointing them into the air and with fourteen shots at his disposal, he began firing.

Bang-Bang-Bang! Bang! Bang! Bang! Bang-Bang-Bang!

The shots rang out on the night air like a series of interrupted explosions. But to the trained ears of the other men of the party—Lieutenant Mackinson, Joe, Jerry and Frank Hoskins—two miles away, they carried their call for help.

It was the S O S of the international code, but in a new sort of wireless—by pistol shots!

Trembling for the results that his desperate action might bring upon them, Slim waited, bending now and then over the unconscious form of Tom Rawle.

But in fifteen more minutes his inventive genius was rewarded. From a considerable distance, but each time more distinctly, now came the repeated call of "Whip-poor-will," and in less time than it seemed possible that they could make it, the other group had returned.

In low commands the lieutenant then directed affairs, and in exactly the way that he had been carried out of the hold of the Everett on the verge of suffocation, so they carried poor Tom Rawle back to their own lines.

And when he had been placed upon a cot in the first emergency hospital, Lieutenant Mackinson hurried off to make his report, in the honor of which all shared.

For not only had they found a location from which to wireless advance-line communications to field headquarters, but they had also intercepted a message, knowledge of which resulted in a quick change of plans by which the Americans were able to beat the enemy at his own game on the morrow.

"Rawle was suffering more from loss of blood than from any seriousness of the injury itself," the surgeon told them when they asked there of their friend's condition, on their way to their own quarters. "He will be around all right again in a week's time."

And so, much desperate work accomplished on their first night within the firing lines, the lads threw themselves upon their cots to dream of spies and captured Germans and injured soldiers and calls for help by new methods in wireless.

As a consequence, the point of communication which the lieutenant and his aides had established with so much difficulty was now well within the territory held by the American and French fighters. The requirements for a further advance now made it necessary to have another outpost point of communication as near to the enemy trenches as the first one was before the day's battle put the Allies a mile further forward.

And so, except for Tom Rawle, who was resting easy from his hip wound, the same party started out at the same tune for the same purpose on this second night, but with a very much sharpened realization of the obstacles they had to overcome and the chances they faced of being wounded or captured.

"We take an entirely different direction," Lieutenant Mackinson told them, as he looked up from the map he had been studying. "We go to the north and east and as close to the observation trenches as possible."

Now the danger of this can readily be seen from considering what an observation trench is. The front-line trenches of the opposing armies, of course, run in two practically parallel lines. But an observation trench runs almost at right angles with the front-line trenches, and directly toward the enemy trench, so far as it is possible to extend it. The extreme ends of these observation trenches are known as "listening posts," and often they are so close to the enemy lines that the men in the opposing army can be heard talking.

Lieutenant Mackinson and his aides, Joe, Jerry, Slim and Frank Hoskins, were to get their signaling location as near to an enemy listening post as possible! In other words, they were to court discovery in an effort to get just a few feet nearer the enemy than they otherwise would.

They went along much as they had on the preceding night, except, had there been light enough, it might have been noticed that Slim, in his walking, pushed his feet forward cautiously, and then in stepping lifted them high from the ground.

But as luck would have it they had not gone more than two hundred yards when a bullet whizzed within two feet of Jerry's head, followed by a shower of missiles that were directed entirely too close to them for comfort.

Instantly they dropped flat on the ground. In the distance ahead of them they could see three shadows stealthily crawling along toward them.

"Pick your men!" Lieutenant Mackinson ordered, in a whisper. "Fire!"

Their automatics let out a fusillade of bullets. Two of the shadows jumped slightly into the air, and then rolled over. The third man rose and started to run toward the enemy line. Frank Hoskins took deliberate aim and fired. The man dropped and lay still.

"Looks as though we got them," said Lieutenant Mackinson, "but they may be only pretending. Do not move for a few minutes."

While they were thus waiting, the enemy trenches sent up a glaring rocket. It fell shorthand failed to reveal them, but it plainly showed three German soldiers lying prone upon the ground, all of them apparently instantly killed.

"That's the part of it I don't like," muttered Slim with a shudder. "It isn't so bad when you are firing into a whole company or regiment and see men fall. At least, it doesn't seem so bad, for you don't know just which ones you hit and which ones some one else bowled over. But in this individual close-range stuff it leaves a nasty feeling."

"You are right," whispered Frank Hoskins, "but you'd better not talk any more about it now or some Boche may try the same close-range stuff on us."

Warned to silence by the lieutenant, they continued to creep along, only a foot or so at a time, stopping every few minutes to listen intently to see if their presence had been discovered.

On the night before they had been upon fairly level ground, but this night they were in a section that was all hills and hummocks and hollows. They would creep cautiously up the side of one mound, not knowing but that on the other side lay a group of Germans, perhaps out upon a similar mission.

For no one can tell what may happen in No Man's Land—that section belonging to neither side, before and between the front-line trenches of the opposing armies.

"With that star as my guide, I am certain that we have not turned from the proper direction," Lieutenant Mackinson whispered, as they came to a halt in a secluded spot that seemed as safe from attack as from observation. "We have passed the fifth hill. Fifteen more minutes should bring us to the place which Major Jones indicated on the map. It is a sort of natural trench. If we reach it all right we are to string a wire from there to our first observation trench to the northwest of it. I believe that the same place has been used for the same purpose before, during the long time that all this has been contested ground. An outpost there can observe and report every activity of the enemy in daylight, without himself being seen."

They began again to creep forward, now flat upon their stomachs, and only raising themselves from the ground a little way, but at infrequent intervals, in order to make sure of their position and that they were not being watched.

"Listen!" hissed Frank Hoskins, who was a little to the left of where the others were snaking their way along.

They all stopped moving, almost stopped breathing.

"What was it?" Lieutenant Mackinson barely breathed, after several minutes of silence.

Hoskins crawled nearer before he spoke.

"How near are we, Lieutenant?" he asked:

"I should say about a hundred yards."

"Look straight ahead of us when the next rocket goes up," Hoskins suggested.

They had not long to wait for one of the great sky torches to come sailing over the side of the German trench, but from a considerable distance ahead of them.

"Did you notice anything?" Hoskins asked.

"I didn't," whispered the lieutenant. "Did you?"

"I thought I saw half a dozen men," said Joe.

"We'll wait, then, and see," said Lieutenant Mackinson.

In a moment another rocket went up, this time from the American-French side, and it clearly showed what Joe and Frank both had seen.

Six, perhaps seven or eight, men were crawling along, headed toward them.

"They are making for the same place," said Jerry.

"Exactly," replied the lieutenant. "It means that we have got to fight for it. We will have some advantage if we can beat them to the protection of the base of that hummock."

As rapidly as possible they started forward. Lying out flat, they would draw their feet upward and toward them, rising slightly and going forward upon their arms. This action, which put them ahead a few inches every time, they repeated times without number. But it was slow progress at best, and made slower by the interruptions of the rockets.

"We are almost there," Lieutenant Mackinson whispered, "but I think we have been discovered. Lie flat and don't make a move. By keeping my head in the position I have it I can watch that other group. If we have been seen it means a running fight to the mouth of that trench or cave."

Another rocket cut a glaring path across the sky. Again it was from the American-French side and illumined the black shadows strewn along the ground like little clumps of low-growing bushes.

"Ah!" exclaimed the lieutenant suddenly, and then, in the same breath: "Up and at 'em, boys!"

Before the others had an opportunity to realize what had happened, Mackinson was dashing at top speed toward the indicated trench or cave, firing as he went.

As they followed suit, but more careful in their shooting, for fear of hitting him, they realized that the men in the enemy group were doing the same thing—running as fast as they could for the same position.

"Drop!" ordered the lieutenant, and they did so, but it was as if he had issued the order for both sides, for the others were not a second later in seeking the security of the ground.

"Either side may begin playing machine-guns on us at any moment," the young officer whispered, between gasps for breath. "Forward as quickly as possible, and continue firing."

How they ever escaped the enemy bullets as long as they did none of them ever knew, but the men of the other side were just as doggedly determined, and no less courageous, even if three of their number already lay stretched out motionless and useless upon the ground.

And so the battle waged, until both groups were no more than fifty feet away from the mouth of the natural trench. Each moment brought them closer together, with the even more vigorous popping of their guns, for by now it was virtually a hand-to-hand battle.

Only four men now remained upon the side of the Germans, and, so far as numbers were concerned, the Americans seemed to have the advantage by one. But the score was evened an instant later, when one of the Boches "winged" Frank Hoskins, and his right arm fell useless at his side.

But Lieutenant Mackinson squared accounts for Hoskins by putting another German completely out of commission. A prompt return compliment knocked Jerry's revolver out of his hand. At this juncture Slim played a heroic part by laying low another German.

Seeing themselves now outnumbered almost two to one—for apparently they did not know that they had injured Hoskins—the two remaining Boches took one final, despairing survey of the situation, then turned and started on a dead run for their own lines.

Lieutenant Mackinson leveled his revolver at them, held it in that position for a moment, and then—perhaps it was an accident—seemed to elevate it slightly in the air and fired. Certainly neither German was hurt by the bullet, although it did seem to add a little to their haste.

"The position is ours," announced the lieutenant exultantly, and then, suddenly remembering that Frank Hoskins had been hit and that Jerry had dropped his gun, he inquired: "Hurt badly, Frank? And how about you, Jerry?"

"Nothing but a scratch," said Frank. "Took me right on the 'crazy bone' and made me jump for a minute, but it's hardly bleeding now."

"Only hit my gun," announced Jerry, "and I recovered that."

There was no time for further conversation. The Germans had reached their own lines, and a machine-gun was being trained upon the Americans. They rushed headlong to the north side of the little mound, and into the opening of a natural cave.

The earthwork made them as solidly entrenched as though they were behind their own lines, and only heavy shells could dislodge them. But they had work to do, and the nature of it required that they do it quickly.

The entrance faced almost directly north and into No Man's Land, so that the light of an electric flash, such as they all carried, hardly could attract the attention of either side.

"Joe," said the lieutenant, sizing up the situation, "it is not safe to leave the enemy unwatched for a single second. I think it would be well for you to stay on duty outside, while the rest of us rig up the instrument and begin to unspool the wire. Hoskins, you're hurt, so you stay here with Joe. But both of you be mighty careful not to expose yourselves where you'll stop a German bullet."

With Lieutenant Mackinson leading, Jerry just behind him and Slim bringing up the rear, they crossed the five feet of narrow passageway back into the natural dungeon.

The lieutenant switched on his light. Involuntarily and with a startled gesture he stepped back.

"Jumping Jupiter!" exclaimed Jerry, "what's that?"

Slim, peering ahead of the other two, ejaculated something between a shriek and a groan.

Strewn about the ground of that cave, in every conceivable position of misery and torture, were the bodies of half a dozen dead men, all Germans.

The lieutenant's hand that held the light trembled slightly as he stared at the ghastly scene before him, but he was grit and courage right through to the heart.

"This is bad business," he said, "but we are under orders and we must go through with it. We cannot move the bodies out to-night."

He stepped further into the dark hole, and the other two lads followed.

Suddenly from behind them there was a grumbling, roaring crash, pierced by a cry of warning from Joe, outside.

The three whirled around, and for a moment no one could utter a word.

The mouth of the dungeon had completely caved in!

"Trapped!" gasped Jerry, who was the first to find his voice.

Even the lieutenant seemed dazed.

"Trapped," echoed Slim, "in the cave of death."

Slim, catching his meaning, snatched a rifle from beside one of the bodies, and with the butt of it began pounding frantically upon the side of the cave where the entrance had been.

There was no answering knock.

"Joe," shouted Jerry in a frenzied tone. "Joe! Can you hear me?"

No answer came, either from Joe or Frank.

"Pinned under tons of that stuff," gasped Slim, the words trembling upon his lips and a tear trickling down his cheek.

"I do not think so," the lieutenant assured them. "Both Joe and Frank were upon the outside when we entered."

"But they would try to get us out," said Jerry. "If they were out there they would give us some sort of signal that they were trying to help us."

"We might not be able to hear them," answered the lieutenant, even against his own judgment. "But look at it this way. Even though they never were inside here, they had a fair idea of what the place was like. They knew from that that we needed help, and needed it quickly. If one went alone, and anything happened to him on the way, the other might wait here indefinitely, not knowing whether he had got assistance or not. By going together they took the safest course."

And Lieutenant Mackinson's reasoning was correct. That was exactly the way Joe and Frank had figured it out, and, the latter forgetting all about his own wound, they had started as fast as they could for the American front.

"Keep cool, conserve your energy, and I feel certain everything will be all right," the lieutenant told the two friends with whom, in such a short time, he already had gone through so many harrowing experiences.

At that very same moment, a quarter of a mile away, Joe brought his companion to a halt, took out his flashlight, and, facing the American line, began making and breaking the connection in a way to give a number of short, even flashes.

Presently a light appeared, was extinguished and appeared again, at the edge of the American-French lines.

Joe had resorted to another sort of wireless—the "blinker"—and, not knowing the call signal for the station he was nearest, had given the prescribed call in such a case, a series of short flashes, or dots. The station had acknowledged, and he began sending his message out of the little battery in his hand:

"Americans. Three of party caught in cave-in. Need help."

And the answer was flashed back in the same code:

"Approach. Keep light on. Countersign."

Following these instructions, with Joe in the lead with the flashlight held out in front of him, they dashed on to the trenches. They gasped out the countersign, and were escorted by a sentry to the quarters of the officer of that particular section.

In a few words they told him what had happened.

Without an instant's delay the latter, a colonel of artillery, reached for his telephone.

"Ask Captain Hallowell to come here immediately," he said, and severed the connection.

He seemed already to have decided upon some sort of a plan, and his decisive manner gave the two lads a feeling of confidence in him. He reached into a drawer of his desk and drew out a large map. He ran his fingers across it and then came to a stop at a little black dot which appeared just in the angle of two converging red lines.

"Is that it?" he asked, turning to Jerry and Frank.

They examined the map carefully for a moment and then told him that it was.

Just then Captain Hallowell entered. His boots were spattered with mud, his face was grimy, and his eyes were bloodshot, indicating that he had been for many hours without sleep.

"Captain," said the colonel bluntly, "these young men are of the Signal Corps, as you you can see. They were detailed to-night to establish an outpost wire communication to Hill No. 8. You know it?"

"Very well, sir," the captain replied, his interest increasing.

"Well," continued the colonel, "they got there all right. But the other three in the party had hardly entered that hole when the entrance caved in."

"Great Scott!" ejaculated the captain. "I know that cavern. They can't last there long."

"Exactly," affirmed the colonel. "What is your suggestion?"

For a full moment Captain Hallowell was silent. "There is only one way," he said finally, "and that is a dangerous way. Blast them out."

"Blast them out?" repeated the colonel, but apparently without surprise. "How?"

"It would take too long to dig them out," Captain Hallowell answered. "And, besides, that could hardly be done without some sort of light, and that would attract enemy fire. There is but one chance, and that is to blast them out with one of our big guns!"

"Can you do it?" the colonel demanded again, in his blunt, insistent way.

"I will do my utmost to save them, sir," Captain Hallowell replied.

"Very well, then," answered his superior officer. "If you feel certain that is the only way, go ahead. Personally, knowing the place as I do, I see no other method myself. Have you the range?"

"I did have, sir," said Captain Hallowell, "but in such a delicate matter as this it would be necessary to be absolutely accurate. We have been firing practically all day, and the position of the guns changes slightly, of course. I would want to find a new and exact range."

He had noticed Frank's limp arm, and he turned to Joe.

"Take this flashlight," he ordered. "It is more powerful than yours. Get back there as quickly as you can, and follow to the letter these directions: Keep between us and that hill until you get to it. Stay on this side of the hill and crawl around toward the entrance until you get to a point where you can place this light, facing us, two feet above the ground and one foot in from the outer surface extremity. Leave it there until you see three quick successive rockets go straight up in the air from here. After that I will give you three minutes in which to get back to a place of safety. I'll put that flashlight out of business, and I think I can liberate your friends."

"Is your injury a serious one?" the colonel demanded of Frank.

"Very slight, sir. Only a flesh wound," Frank responded eagerly.

"Then take this light," the colonel ordered, "and follow him at a distance of a hundred yards. If anything should happen to your friend, you follow the directions you have just heard."

"Yes, sir," the lads responded in unison, and, with a hasty salute, were off.

Three times did Joe drop to the ground, as a shadow seemed to move somewhere out in the distance before him. But each time he was up and off again almost upon the instant, thinking of his own safety only as that of his three friends depended upon it.

And what of those inside?

Even the courageous Lieutenant Mackinson was beginning to show the anxiety he felt, while Jerry and Slim, despite their bravest efforts, gave way to occasional expressions of the horror of the thing.

They had pounded upon the walls until they had been overcome with despair, and then they had set to work digging with the only instruments at hand—the bayonets on the German rifles.

But soon they realized that this, too, was as hopeless as the pounding, for it further exhausted the energy which the foul air was rapidly sapping, without making any apparent opening in the thick earthen wall that surrounded them.

"Well," said Slim at last, gulping back his nausea, and smiling almost in his old time way, "I'm as anxious as anybody to keep up hope to the last. But if this is to be our end, I guess we can face it as Americans should."

"Bravo!" exclaimed Lieutenant Mackinson, "I always knew that each one of you fellows had the right sort of stuff in you."

And Jerry, too, slapped him affectionately on the back.

"Slim," he said, smiling over at his chum, and ready for his pun, even under such circumstances, "my head is feeling a 'trifle heavy,' but I'm game to stand up to the last."

Thus they sat down to wait—for just what, they did not know—while at that very moment, four feet away from them on the other side of the wall, faithful Joe was setting up the flashlight exactly according to directions.

For a few seconds he waited, and then, three times in quick succession, a rocket went into the air from just behind the American lines.

Over there Captain Hallowell himself found the range, submitted it to his most expert gunner, who verified it, and then they waited for the three minutes to elapse, during which Joe was to seek a place of safety.

It was in that interval, too, that Fate intervened for those within the cave, for they were sitting with their backs to the very point against which the shell was to be directed.

"We need all our strength," Lieutenant Mackinson was saying. "So long as possible we want to remain in full possession of our senses. The air is purer near the floor. I think it would be better to lie down."

And following his suggestion and example, the other two stretched themselves out in the middle of the cavern.

Within the American lines, at that point where a regiment of heavy artillery was stationed, Captain Hallowell raised his hand in signal to his gunner. Out on the parapet of the front trench an anxious colonel was standing, regardless of all danger, a pair of powerful glasses to his eyes. His vision was focused upon a little light far out in No Man's Land.

Two hundred feet away from that light Joe and Frank Hoskins lay prone upon the ground, silent, impatient, fearful, hoping.

With a quick motion the artillery captain swung his outstretched arm downward. There was a roar, a flash, and a great shell tore through the air. Out in No Man's Land there was a second explosion as the shell hit, and the target—a flashlight—was blown to atoms.

Over in the German trenches a sentinel chuckled at the thought of another wasted American shell, but out of the hole that that shell had torn three pale, haggard, and exhausted youths were crawling to safety and God's fresh air. And across No Man's Land dashed two pals to greet them.

American determination and American marksmanship had saved three American lives. The German sentinel might have his laugh if he liked.

It was hours later before the three who had been imprisoned learned how their rescue had been effected; but they got an inkling of it as they came within four hundred yards of the American-French front.

"What are you doing?" Lieutenant Mackinson had asked, as Joe brought the party to a stop.

"Just a moment and you will see," Joe had responded.

And, first in wonder and then with a dawning understanding, the other three read off his flashed message:

"Signal Corps men, and whole party safe."

For several days the American and French aviators had been reporting heavy German formations in that region, evidently with the design of a terrific assault, but the allied commanders had not expected it so soon, and in truth they were not fully prepared for it.

It was a surprise attack in every sense of the word, with all the terrible carnage that such a battle brings.

Shortly before midnight of the preceding night a terrible bombardment had been directed against the American-French trenches, and their hidden artillery to the rear of them. This was kept up for about seven hours, and the duel of heavy guns shook the earth like a quake and was deafening.

Then, just as dawn was breaking, the infantry onslaught, participated in at some points by detachments of cavalry, began.

For three hours the Americans and the French fought stubbornly and with every ounce of strength and determination. Whole regiments and even brigades were wiped out on both sides, but the Boches, who had prepared every detail of the assault for weeks, were readier than their opponents and filled the gaps in their lines more quickly.

By noon it became apparent that the sacrifice of lives was becoming too great to warrant the Allies trying to hold their first-line trenches much longer, and that they must give them up, at least until they could re-mobilize their forces for a counter-attack.

The order was therefore given for those in the rear, including food and ammunition trains, field hospitals, etc., to fall back, in order to make way for the strategic retreat of those on the front when the moment for that retreat came.

Everything moved like clockwork, and with the greatest possible speed. And throughout it all men on both sides were shooting, shouting, shrieking, fighting, falling, while others, trapped in their dug-outs, either surrendered or fought desperately on until they fell wounded or lifeless before superior numbers.

Half a mile in the air, apparently over a point midway between what had been the first-line trenches of the opposing armies, a stationary balloon showed where Jerry and an observation officer were doing duty on that fateful day. Jerry was operating a telephone that ran directly to division headquarters, and hardly a moment passed when he was not repeating some observation of the other man in the basket with him, or relaying to him a query from the commander below.

Every detail of that tremendous battle Jerry knew. His own occasional glimpses over the side informed him of the temporary reverses his own army was suffering, while the remarks of the officer told him where the Germans were meeting their bitterest repulses, where they were drawing up their heaviest forces of reserves, what quick changes were being made in their general line of formation, and how far back their forces seemed to extend.

Slim Goodwin, busy as he was with the wireless at headquarters, found time for occasional glances upward at that balloon, to make sure that thus far his friend was still safe.

And even in the thick of machine-gun fire and shrapnel, where Lieutenant Mackinson, Joe, Frank Hoskins and two or three others were laying a new line of communication, the wavering, swaying target was watched from time to time, and speculations made as to how long it could remain without being punctured by a bullet, thus forcing its two occupants to resort to their parachutes to make a landing.

It was now well into the afternoon. The Germans had swept into the places vacated by the Americans and French, and still the battle raged. It was now that Slim began to wait anxiously for the new development, which his familiarity with the secret orders issued made him know was coming.

And finally it did come, and in a way that staggered the Boches.

The Americans and French had retreated to a general line which permitted a quick re-mobilization to the best advantage. There their front-line ranks held firm, while the new formation was being effected behind them. It was about four o'clock in the afternoon when this was complete.

Then, in concerted action, the lines opened at alternate points, and pairs, dozens, scores of the huge armored tanks rolled through, their big guns already blazing shells into the ranks of the disconcerted enemy.

Nothing could halt them. They climbed trench parapets, descended into gullies, came out upon level land, and over their whole path swept destruction to the Germans.

Unable either to resist or to stop the progress of the tanks, which were followed by whole divisions of infantry, the Boches were forced to retreat and not only abandon every foot of the ground they had gained, but to sacrifice a part of their own first line as well.