sound of a bugle blowing the call to arms. Both were quickly on their feet and dashed through the darkness to where they could make out the form of their commander, surrounded by other members of his staff.

"Something up!" cried Hal as they hurried forward.

"Probably a night attack," said Chester. "General French may be planning to carry some of the enemy's trenches by assault."

"Guess you are right," replied Hal briefly.

They took their places among the others of the British leader's staff and were received with nods of welcome and some expressions of astonishment. They had friends among the British officers, many of whom, because of their long absence, had mourned them as dead.

The lads let their eyes roam about. Troops, troops, troops! Nothing but troops, as far as the eye could see. Cavalry, artillery and infantry in solid masses on every side; officers darting hither and thither delivering sharp orders. It was an impressive sight.

An officer on horseback dashed up to General French and the two held a short conversation. As the rider turned and was about to make off again the lads recognized him.

"Major Derevaux!" shouted Hal, taking a step forward.

The officer wheeled in his saddle. He recognized the two lads in an instant, and reined in.

"Hello, boys," he called back. "I heard you were dead. Glad to see you again."

Without further words, but with a wave of his hand, the French officer put spurs to his horse and dashed out of sight in the darkness.

"Wonder what he is doing here?" said Hal. "He was attached to General
Joffre's staff when we left. Remember?"

"Yes," replied Chester. "Must be some momentous move under way."

Other officers now began to appear. They dashed up to the British commander, made their reports and immediately dashed away again.

"Lieutenant Paine! Lieutenant Crawford!"

It was General French summoning them and the boys approached and came to attention. Because of past experience, both lads realized instantly that the General had some ticklish work cut out and that he had selected them to carry it through.

"Take a troop of cavalry," came the command, "and make a reconnoissance of the northeast!"

Quickly two officers nearby sprang from their horses and offered them to the lads, for the latter had not yet had time to find steeds. The lads sprang into the saddle, saluted their commander, and dashed away. To the nearest cavalry force they hurried, where upon repeating General French's order to the commander, they soon had a troop at their disposal.

A troop of cavalry is composed of one hundred men. It is usually commanded by a captain.

Now it is very unusual for a commanding officer to have two lieutenants on his staff, as had General French in the persons of Hal and Chester; but the General had commissioned them as such on the spur of the moment, and when they took command of the troop they consequently, for the time, superseded the captain in command—for they were the personal representatives of the General himself.

The two lads placed themselves at the head of the troop and rode forward at a rapid trot. Past dense masses of infantry, battery after battery of heavy artillery and troop upon troop of cavalry they rode toward the northeast.

They were not yet at the front of the long battle line, for General French had his headquarters well back, but still close enough to be in constant danger from the enemy's artillery fire.

From a trot the troop broke into a gallop, and soon were beyond the farthest trenches. Skirting this at the extreme north—close to the sea—they progressed still further toward the enemy. It was the boys' duty, if possible, to find out the position of the German forces at this point and to determine their numbers; also the strategic positions that could be used by either army.

Now an order was given for the troop to spread out, and, leaving the road, the two lads led their men into the woods, where they could advance with less danger of being seen. They had not been ordered forward to give battle, and there would be no fighting unless it became necessary in order that their mission might be successful.

But, as in most missions upon which the lads had been dispatched, there was to be fighting; and these British were not the men to turn their backs upon the enemy without giving them a warm reception.

From the shelter of the sand dunes there came suddenly a fusillade. Two
British troopers reeled in their saddles and tumbled to the ground.

CHAPTER II.

A BIT OF HISTORY.

While Hal and Chester and their troop of British cavalry are preparing to meet this unexpected attack, it will be well to introduce here a few words relating to the positions of the gigantic armies battling in France and Belgium.

The war had now been in progress for five months. From the time that the
Allies had braced and checked the Germans in their rapid advance upon
Paris, and had assumed the offensive themselves, they had progressed
consistently, if slowly.

The Germans contested every inch of the ground, and all along the great battle line, stretching out for almost four hundred miles, the fighting had been terrific. Day after day, week after week, month after month the terrible struggle had raged incessantly. The losses of all four armies, German, British, French and Belgian, had been enormous, although, up to date, it was admitted that the Germans had suffered the worst.

The conflict raged with advantage first to one side and then to the other. Assaults and counter-assaults were the order of the day. From Ostend, on the North Sea, now in the hands of the Germans, to the southern extremity of Alsace-Lorraine, the mighty hosts were locked in a death grapple; but, in spite of the fearful execution of the weapons of modern warfare, there had been no really decisive engagement. Neither side had suffered a severe blow.

In the North the Allies were being given powerful aid by a strong British fleet, which hurled its shells upon the Germans infesting that region, thus checking at the same time the threatened advance of the Kaiser's legions upon Nieuport and Dunkirk, which the Germans planned to use as naval bases for air raids on England.

The mighty siege and field guns of the Germans—which had been used with such telling effect upon Liège, Brussels, Antwerp and Ostend, battering the fortifications there to bits in practically no time at all—while immense in their power of destruction, were still not a match for the longer range guns mounted by the British battleships. Consequently, long-range artillery duels in the north had been all in favor of British arms.

Terrific charges of the British troops, of whom there were now less than half a million—Scotch, Irish, Canadians and Indians included—on the continent, had driven the Germans from Dixmude, Ypres and Armentières, captured earlier in the war. Ostend had been shelled by the British fleet, and a show of force had been made in that vicinity, causing the Germans to believe that the Allies would attempt to reoccupy this important seaport.

Farther south the French also had met with some success. From within striking distance of Paris the invaders had been driven back to the Marne, and from the Marne to the northern and eastern shores of the Aisne.

But here the German line held.

The fighting along the Aisne,