The sound of cannonading grew fiercer and fiercer, as they advanced, and the undertone of rifle fire more perceptible. It was evident that the Germans were rapidly getting more and more guns into action, and that the infantry attack was also being hotly pressed. Below them in the valley, they caught glimpses from time to time, as the trees opened out a little, of the gray-clad host marching steadily forward, as though to overwhelm the forts by sheer weight of numbers; and then, as they came out above a rocky bluff, they saw a new sight—an earnest that the Belgians were fighting to some purpose.

In a level field beside the road a long tent had been pitched, and above it floated the flag of the Red Cross. Toward it, along the road, came slowly a seemingly endless line of motor ambulances. Each of them in turn stopped opposite the tent, and white-clad assistants lifted out the stretchers, each with its huddled occupant, and carried them quickly, yet very carefully, inside the tent. In a moment the bearers were back again, pushed the empty stretchers into place, and the ambulance turned and sped swiftly back toward the battlefield. Here, too, it was evident that there was admirable and smoothly-working system—a system which alleviated, so far as it was possible to do so, the horror and the suffering of battle.

Stewart could close his eyes and see what was going on inside that tent. He could set the stripping away of the clothing, the hasty examination, the sterilization of the wound, and then, if an operation was necessary, the quick preparation, the application of the ether-cone and the swift, unerring flash of the surgeon's knife.

"That's where I should be," he said, half to himself, "I might be of some use there!" And then he turned his eyes eastward along the road. "Great heavens! Look at that gun."

Along the road below them came a monstrous cannon, mounted on a low, broad-wheeled truck, and drawn by a mighty tractor. It was of a girth so huge, of a weight evidently so tremendous, that it seemed impossible it could be handled at all, and yet it rolled along as smoothly as though it were the merest toy. Above it stretched the heavy crane which would swing it into the air and place it gently on the trunnions of its carriage. Drawn by another tractor, the carriage itself came close behind—more huge, more impressive if possible, than the gun itself. Its tremendous wheels were encircled with heavy blocks of steel, linked together and undulating along the road for all the world like a monster caterpillar; its massive trail seemed forged to withstand the shock of an earthquake.

"So that is the surprise!" murmured the girl beneath her breath.

And she was right. This was the surprise which had been kept so carefully concealed—the Krupp contribution to the war—the largest field howitzer ever built, hurling a missile so powerful that neither steel nor stone nor armored concrete could stand against it.

In awed silence, the two fugitives watched this mighty engine of destruction pass along the road to its appointed task. Behind it came a motor truck carrying its crew, and then a long train of ammunition carts filled with what looked like wicker baskets—but within each of those baskets lay a shell weighing a thousand pounds! And as it passed, the troops, opening to right and left, cheered it wildly, for to them it meant more than victory—it meant that they would, perhaps, be spared the desperate charge with its almost certain death.

Scarcely had the first gone by, when a second gun came rolling along the road, followed by its crew and its ammunition-train; and then a third appeared, seemingly more formidable than either of the others.

"These Germans are certainly a wonderful people," said Stewart, following the three monsters with his eyes as they dwindled away westward along the road. "They may be vain and arrogant and self-confident; apparently they haven't much regard for the rights of others. But they are thorough. We must give them credit for that! They are prepared for everything."

"Yes," agreed his companion; "for everything except one thing."

"And that?"

"The spirit of a people who love liberty. Neither cannon nor armies can conquer that! The German Staff believed that Belgium would stand aside in fear."

"Surely you don't expect Belgium to win?"

"Oh, no! But every day she holds the German army here is a battle won for France. Oh, France will honor Belgium now! See—the army has been stopped. It is no longer advancing!"

What was happening to the westward they could not see, or even guess, but it was true that the helmeted host had ceased its march, had broken ranks, and was stacking arms and throwing off its accouterments in the fields along the road. The halt was to be for some time, it seemed, for everywhere camp-kitchens were being hauled into place, fires started, food unloaded.

"Come on! come on!" urged the girl. "We must reach the Meuse before this tide rolls across it."

They pressed forward again along the wooded hillside. Twice they had to cross deep valleys which ran back into the mountain, and once they had a narrow escape from a cavalry patrol which came cantering past so close upon their heels that they had barely time to throw themselves into the underbrush. They could see, too, that even in the hills caution was necessary, for raiding parties had evidently struck up into them, as was proved by an occasional column of smoke rising from a burning house. Once they came upon an old peasant with a face wrinkled like a withered apple, sitting staring down at the German host, so preoccupied that he did not even raise his eyes as they passed. And at last they came out above the broad plain where the Vesdre flows into the Meuse.

LiÈge, with its towers and terraced streets, was concealed from them by a bend in the river and by a bold bluff which thrust out toward it from the east—a bluff crowned by a turreted fortress—perhaps the same they had seen the night before—which was vomiting flame and iron down into the valley.

The trees and bushes which clothed its sides concealed the infantry which was doubtless lying there, but in the valley just below them they could see a battery of heavy guns thundering against the Belgian fort. So rapidly were they served that the roar of their discharge was almost continuous, while high above it rose the scream of the shells as they hurtled toward their mark. There was something fascinating in the precise, calculated movement of the gunners—one crouching on the trail, one seated on either side of the breech, four others passing up the shells from the caisson close at hand. Their officer was watching the effect of the fire through a field-glass, and speaking a word of direction now and then.

Their fire was evidently taking effect, for it was this battery which the gunners in the fort were trying to silence—trying blindly, for the German guns were masked by a high hedge and a strip of orchard, and only a tenuous, quickly-vanishing wisp of white smoke marked the discharge. So the Belgian gunners dropped their shells hither and yon, hoping that chance might send one of them home.

They did not find the battery, but they found other marks—a beautiful white villa, on the first slope of the hillside, was torn asunder like a house of cards and a moment later was in flames; a squad of cavalry, riding gayly back from a reconnoissance down the river, was violently scattered; a peasant family, father and mother and three children, hastening along the road to a place of safety, was instantly blotted out.

It was evident now that the Meuse was the barrier which had stopped the army. Far up toward LiÈge were the ruins of a bridge, and no doubt all the others had been blown up by the Belgians.

Down by the river-bank a large force of engineers were working like mad to throw a pontoon across the swift current. The material had already been brought up—heavy, flat-bottomed boats, carried on wagons drawn by motor-tractors, great beams and planks, boxes of bolts—everything, in a word, needed to build this bridge just here at a point which had no doubt been selected long in advance! The bridge shot out into the river with a speed which seemed to Stewart almost miraculous. Boat after boat was towed into place and anchored firmly; great beams were bolted into position, each of them fitting exactly; and then the heavy planks were laid with the precision and rapidity of a machine. Indeed, Stewart told himself, it was really a machine that he was watching—a machine of flesh and blood, wonderfully trained for just such feats as this.

"Look! look!" cried the girl, and Stewart, following her pointing finger, saw an aËroplane sweeping toward them from the direction of the city. Evidently the defenders of the fort, weary of firing blindly at a battery they could not see, were sending a scout to uncover it.

The aËroplane flew very high at first—so high that the two men in it appeared the merest specks, but almost at once two high-angle guns were banging away at it, though the shells fell far short. Gradually it circled lower and lower, as if quite unconscious of the marksmen in the valley, and as it swept past the hill, Stewart glimpsed the men quite plainly—one with his hands upon the levers, the other, with a pair of glasses to his eyes, eagerly scanning the ground beneath.

And then Stewart, happening to glance toward the horizon, was held enthralled by a new spectacle. High over the hills to the east flew a mammoth shape, straight toward the fort. Its defenders saw their danger instantly, and hastily elevating some of their guns, greeted the Zeppelin with a salvo. But it came straight on with incredible speed, and as it passed above the fort, a terrific explosion shook the mountain to its base. Stewart, staring with bated breath, told himself that that was the end, that not one stone of that great fortress remained upon another; but an instant later, another volley sent after the fleeing airship told that the fort still stood—that the bomb had missed its mark.

The aËroplane scouts, their vision shadowed by the broad wings of their machine, had not seen the Zeppelin until the explosion brought them sharp round toward it. Then, with a sudden upward swoop, they leaped forward in pursuit. But nothing could overtake that monster,—it was speeding too fast, it was already far away, and in a moment disappeared over the hills to the west. So, after a moment's breathless flight, the biplane turned, circled slowly above the fort, and dropped down toward the town behind it.

Five minutes later, a high-powered shell burst squarely in the midst of the German battery, disabling two of the guns. At once the horses were driven up and the remaining guns whirled away to a new emplacement, while a passing motor ambulance was stopped to pick up the wounded.

Stewart, who had been watching all this with something of the feelings of a spectator at some tremendous panorama, was suddenly conscious of a mighty stream of men approaching the river from the head of the valley. A regiment of cavalry rode in front, their long lances giving them an appearance indescribably picturesque; behind them came column after column of infantry, moving like clock-work, their gray uniforms blending so perfectly with the background that it was difficult to tell where the columns began or where they ended. Their passage reminded Stewart of the quiver of heat above a sultry landscape—a vibration of the air scarcely perceptible.

All the columns were converging on the river, and looking toward it, Stewart saw that the bridge was almost done. As the last planks were laid, a squadron of Uhlans, which had been held in readiness, dashed across, and deploying fanshape, advanced to reconnoiter the country on the other side.

"That looks like invasion in earnest!" said Stewart.

The girl nodded without replying, her eyes on the advancing columns. The cavalry was the first to reach the bridge, and filed rapidly across to reËnforce their comrades; then the infantry pressed forward in solid column. Stewart could see how the boats settled deep in the water under the tremendous weight.

High above all other sounds, came the hideous shriek of a great shell, which flew over the bridge and exploded in the water a hundred yards below it. A minute later, there came another shriek, but this time the shell fell slightly short. But the third shell—the third shell!

Surely, Stewart told himself, the bridge will be cleared; that close-packed column will not be exposed to a risk so awful. But it pressed on, without a pause, without a break. What must be the soldiers' thoughts, as they waited for the third shell!

Again that high, hideous, blood-curdling shriek split through the air, and the next instant a shell exploded squarely in the middle of the bridge. Stewart had a moment's vision of a tangle of shattered bodies, then he saw that the bridge was gone and the river filled with drowning men, weighed down by their heavy accouterments. He could hear their shrill cries of terror as they struggled in the current; then the cries ceased as the river swept most of them away. Only a very few managed to reach the bank.

Stewart hid his face in his trembling hands. It was too hideous! It could not be! He could not bear it—the world would not bear it, if it knew!

A sharp cry from his companion told him that the awful drama was not yet played to an end. She was pointing beyond the river, where the cavalry and the small body of infantry which had got across seemed thrown into sudden confusion. Horses reared and fell, men dropped from their saddles. The infantry threw themselves forward upon their faces; and then to Stewart's ears came the sharp rattle of musketry.

"The Belgians are attacking them!" cried the girl. "They are driving them back!"

But that cavalry, so superbly trained, that infantry, so expertly officered, were not to be driven back without a struggle. The Uhlans formed into line and swept forward, with lances couched, over the ridge beyond the river and out of sight, in a furious charge. But the Belgians must have stood firm, for at the end of a few moments, the troopers straggled back again, sadly diminished in numbers, and rode rapidly away down the river, leaving the infantry to its fate.

Meanwhile, on the eastern bank of the river, a battery of quick-firers had already been swung into position, and was singing its deadly tune to hold the Belgians back. Already the men of that little company on the farther side had found a sort of refuge behind a line of hummocks. Already some heavier guns were being hurried into position to defend the bridge which the engineers began at once to rebuild farther down the stream, where it would be better masked from the fort's attack.

Evidently the Belgians did not intend to enter that deadly zone of fire, and the fight settled down to a dogged, long-distance one.

"We cannot get across here," said the girl at last. "We shall have to work our way downstream until we are past the Germans. If we can join the Belgians, we are safe."

But to get past the Germans proved a far greater task than they had anticipated. There seemed to be no end to the gray-clad legions. Brigade after brigade packed the stretch of level ground along the river, while the road was crowded with an astounding tangle of transport wagons, cook wagons, armored motors, artillery, tractors, ambulances, and automobiles of every sort, evidently seized by the army in its advance.

As he looked at them, Stewart could not but wonder how on earth they had ever been assembled here, and, still more, how they were ever going to be got away again. Also, he thought, how easily might they be cut to pieces by a few batteries of machine-guns posted on that ridge across the river! Looking across, he saw that the army chiefs had foreseen that danger and guarded against it, for a strong body of cavalry had been thrown across the river to screen the advance, while along the bank, behind hasty but well-built intrenchments, long lines of artillery had been massed to repel any attack from that direction.

But no attack came. The little Belgian army evidently had its hands full elsewhere, and was very busy indeed, as the roar of firing both up and down the river testified. And then, as the fugitives walked on along the hillside, they saw that one avenue of advance would soon be open, for a company of engineers, heavily guarded by cavalry, and quick-firers, was repairing a bridge whose central span had been blown up by the Belgians as they retreated.

The bridge had connected two little villages, that on the east bank dominated by a beautiful white chÂteau placed at the edge of a cliff. Of the villages little remained but smoking ruins, and a flag above the chÂteau showed that it had been converted into a staff headquarters.

Where was the owner of the chÂteau, Stewart wondered, looking up at it. Where were the women who had sat and gossiped on its terrace? Where were all the people who had lived in those two villages? Wandering somewhere to the westward, homeless and destitute, every one of them—haggard women and hungry children and tottering old men, whose quiet world had turned suddenly to chaos.

"Well," he said, at last, "it looks as if we shall have to wait until these fellows clear out. We can't get across the river as long as there is a line like that before it."

"Perhaps when they begin to advance, they will leave a break in the line somewhere," his companion suggested. "Or perhaps we can slip across in the darkness. Let us wait and see."

So they sat down behind the screen of a clump of bushes, and munched their apples, while they watched the scene below. Stewart even ventured to light his pipe again.

A flotilla of boats of every shape and size, commandeered, no doubt, all up and down the river, plied busily back and forth, augmenting the troops on the other side as rapidly as possible; and again Stewart marveled at the absolute order and system preserved in this operation, which might so easily have become confused. There was no crowding, no overloading, no hurrying, but everywhere a calm and efficient celerity. A certain number of men entered each of the boats,—leading their horses by the bridle, if they were cavalry,—and the boats pushed off. Reluctant horses were touched with a whip, but most of them stepped down into the water quietly and without hesitation, showing that they had been drilled no less than their masters, and swam strongly along beside the boat. On the other shore, the disembarkation was conducted in the same unhurried fashion, and the boat swung back into the stream again for another load.

But a great army cannot be conveyed across a river in small boats, and it was not until mid-afternoon, when the repairs on the bridge were finished, that the real forward movement began. From that moment it swept forward like a flood—first the remainder of the cavalry, then the long batteries of quick-firers, then regiment after regiment of infantry, each regiment accompanied by its transport. Looking down at the tangle of wagons and guns and motors, Stewart saw that it was not really a tangle, but an ordered arrangement, which unrolled itself smoothly and without friction.

The advance was slow, but it was unceasing, and by nightfall at least fifteen thousand men had crossed the river. Still the host encamped along it seemed as great as ever. As one detachment crossed, another came up from somewhere in the rear to take its place. Stewart's brain reeled as he gazed down at them and tried to estimate their number; and this was only one small corner of the Kaiser's army. For leagues and leagues to north and south it was pressing forward; no doubt along the whole frontier similar hosts were massed for the invasion. It was gigantic, incredible—that word was in his thoughts more frequently than any other. He could not believe his own eyes; his brain refused to credit the evidence of his senses.

Each unit of this great array, each company, each squad, seemed to live its own life and to be sufficient unto itself. Stewart could see the company cooks preparing the evening meal; the heavy, wheeled camp-stoves were fired up, great kettles of soup were set bubbling, broad loaves of dark bread were cut into thick slices; and finally, at a bugle call, the men fell into line, white-enameled cups in hand, and received their rations. It seemed to Stewart that he could smell the appetizing odor of that thick soup—an odor of onions and potatoes and turnips.

"Doesn't it make you ravenous?" he asked. "Wouldn't you like to have some real solid food to set your teeth into? Raw eggs and apples—ugh!"

"Yes, it does," said the girl, who had been contemplating the scene with dreamy eyes, scarcely speaking all the afternoon. "The French still wear the uniform of 1870," she added, half to herself; "a long bulky blue coat and red trousers."

"Visible a mile away—while these fellows melt into the ground at a hundred yards! If Germany wins, it will be through forethought!"

"But she cannot win!" protested the girl, fiercely. "She must not win!"

"Well, all I can say is that France has a big job ahead!"

"France will not stand alone! Already she has Russia as an ally; Belgium is doing what it can; Servia has a well-tried army. Nor are those all! England will soon find that she cannot afford to stand aside, and if there is need, other nations will come in—Portugal, Rumania, even Italy!"

Stewart shook his head, skeptically.

"I don't know," he said, slowly. "I know nothing about world-politics, but I don't believe any nation will come in that doesn't have to!"

"That is it—all of them will find that they have to, for Prussian triumph means slavery for all Europe—for the Germans most of all. It is for them as much as for herself that France is fighting—for human rights everywhere—for the poor people who till the fields, and toil in the factories, and sweat in the mines! And civilization must fight with her against this barbarian state ruled by the upturned mustache and mailed fist, believing that might makes right and that she can do no wrong! That is why you and I are fighting on France's side!"

"If nobody fights any harder than I——"

She stopped him with a hand upon his arm.

"Ah, but you are fighting well! One can fight in other ways than with a rifle—one can fight with one's brains."

"It is your brains, not mine, which have done the fighting in this campaign," Stewart pointed out.

"Where should I have been but for you? Dead, most probably, my message lost, my life-work shattered!"

He placed his hand quietly over hers and held it fast.

"Let us be clear, then," he said. "It is not for freedom, or for any abstract ideal I am fighting. It is for you—for your friendship, for your——"

"No, it is for France," she broke in. "I am not worth fighting for—I am but one girl among many millions. And if we win—if we get through——"

She paused, gazing out through the gathering darkness with starry eyes.

"Yes—if we get through," he prompted.

"It will mean more to France than many regiments!" and she struck the pocket which contained the letters. "Ah, we must get through—we must not fail!"

She rose suddenly and stretched her arms high above her head.

"Dear God, you will not let us fail!" she cried. Then she turned and held out a hand to him. "Come," she said, quietly; "if we are to get across, it must be before the moon rises."