They rose higher and higher, climbing in spirals, until Dick had completely lost his bearings. The night was cloudy, and there were no stars to help him, and before long they had passed through the first layer of low hanging clouds, so that he was denied the aid of lights and towns below. Then when they had thus made it impossible for anyone below to detect them, Stepan gave his motor full play and the real flight began. Dick thought he had never in his life known a sensation so glorious as this swift gliding along through the air. But he soon appreciated the comfort that came from the thick clothes upon which his chum had insisted. Despite the weight of the things, he was far from being hot in that long night flight.

Sometimes he slept. He was aroused once when they descended, but the country was wholly unfamiliar to him, and they were soon off again. But with morning came a stunning surprise. The sun was visible now, and Dick saw that they had been flying northeast! He had supposed that they would head for the Servian army, but he guessed now, as he saw snow capped mountains before them, that they had taken an entirely different course. And his surprise was vastly increased when a strange sound assailed his ears.

"Ah!" cried Stepan, exulting. "It is all right!"

Dick followed Stepan's pointing finger with his eyes, and now he saw the source of the firing that had so astonished him. It was in front of him, on the plain between them and the mountains, which were far away still, though they seemed so near.

"What troops are those? And where are we?" he cried.

"We have flown across Hungary in the night, and those are Hungarian regiments, giving way before the advance of Russian troops who have come through the passes from Galicia!" cried Stepan. "But that is not what counts! Look down there—to the right!"

Dick looked. What he saw was a small village that had suddenly become a city. Trains were drawing in, and a dozen or more sidings contained strings of cars that had evidently arrived during the night. As they looked a train stopped and soldiers poured from it.

"Do you understand? Can you realize what that means, Dick?" cried Stepan. "They are sending reËnforcements from Servia! Those troops were among those who were attacking us. The Russian invasion through the passes has brought them back! That is what we came for—to learn if that were so!"

"Oh, I do understand now!" cried Dick, as a great light burst on his mind. He saw it all. This was what Servia had been hoping for; a weakening of the forces massed against her. No wonder it had been all-important to know if the reËnforcement had really been sent! Then his eye wandered, and he saw something coming through the air—another aeroplane was approaching them.

"Look out, Stepan! Here comes one of their machines!" he cried.

Stepan seized his glass on the instant.

"Yes!" he said. "That is bad luck for it is one of their newer, faster machines! We must try to get away! Here, take this rifle. If she comes so near that she discovers who we really are, we must fight. Aim for the tank. A bullet through that will send them down quickly! But don't fire until I give the word. It is better to run than to fight, if we can."

And now, as if he had not seen the hostile aeroplane, Stepan turned and began to race south, in the direction whence they had come. There followed the most exciting of possible contests—a real race between aeroplanes, not for a prize or a trophy, but with life itself, or liberty at least, as the price of victory or the penalty of defeat.

With the slower, clumsier machine, Stepan still made a wonderful showing. He went up, then down, twisting this way and that, manoeuvering with brilliant skill. The other machine followed, however, and it was gaining constantly, thanks to its better motor. Still it did not fire a shot, for it must have been difficult for the pilot to know what possessed the machine that he chased. It was so obviously an Austrian monoplane, yet its actions were suspicious.

At last Stepan reduced his speed. At the moment they were above the rival birdman, who was climbing to get on a level.

"Now—and aim for the tank!" cried Stepan.

Dick fired. His first bullet went wide, and cut through the wing. But the next one found its mark. They could hear the sharp ping as it struck the metal tank, even above the roar of the two racing engines. And then another—and all three before the enemy could reply.

"Good! We are saved!" cried Stepan.

For the Austrian machine staggered like a bird hit on the wing, reeled, and then plunged downward. One bullet sang past them, dangerously close, but that was all. In a moment they were alone in the heavens, racing toward Servia, while behind them the roar of battle continued.

On and on they flew. They passed over Belgrade and Semlin late in the afternoon, when the sun was sinking. It was dark when they crossed a plain from which great numbers of troops stared up at them. But they were flying very high and very fast, and though two more Austrian aeroplanes began to pursue, there was no danger that they would be caught. And at last, weary, exhausted, they came to earth in the Servian camp.

"Come with me," said Stepan. Willing hands were caring for the aeroplane, and now a staff officer came up.

"You are Stepan Dushan?" he asked. "I am to take you to the general!"

"My companion, too," insisted Stepan.

And so Dick was present when Stepan made his report to the veteran general who commanded the Servian army. He saw the light that came into the leader's eyes when he heard of the arrival of the Austrian troops in Hungary and listened, with admiration, to the sharp fusillade of orders which interrupted Stepan's narrative.

"Now we know what to do!" said the general. "Now we shall fall upon them. The battle will begin to-night! They have been trying to force a battle. Well, they shall have it! Go, now, sleep. In the morning there will be great sights for your eyes!"

And in the morning, indeed, Dick and Stepan were present when King Peter, his snowy hair bared to the wind, rode before his troops.

"The time has come, my children!" said the old king. "The time has come for us to drive the invader from Servian soil! We have had to retreat, and it has been hard! But now—now we can strike! This is the dawn of Servia's greatest day, in victory or defeat! Your old king has come now to see you conquer—or to die among you!"

What a cheer there was as the king spoke! What a roar greeted him! With what eagerness did the troops hail the order to advance!

Already the cannon were thundering. Soon now rifle fire in sullen, crackling volleys broke upon the air. And that day the Austrians learned that they had walked into a trap; that Servia's army had retreated, not because it was beaten, not because it was afraid, but that it might fight, when the time for battle came, on its own chosen ground. From the east came the army that had guarded Belgrade for so long, striking at the Austrian flank. And once more an Austrian defeat became a rout. Once more the Servians pursued.

Dick and Stepan could see only a little of the great struggle. But that little was enough to teach them that they were looking upon history in the making. The battle was one of those crushing, decisive struggles that seldom occur. With defeat the last hope of a successful Austrian invasion of little Servia seemed to be shattered and when the sun went down there was no longer any doubt of the issue.

The Austrians had fought well and bravely, but the Servians had fought with the courage of despair and the cool precision of trained soldiers used to victory, as well. The stars that night looked down upon the abject flight of the Austrian army, split in two parts, scattering its arms, its equipment, everything that would retard the search for safety from the furious pursuit of the Servians.

"We let them have Belgrade—for a few days!" said Stepan, drunk with happiness. "But now we want it for ourselves—our capital is the place to celebrate a victory!"

And so it proved. Two divisions of the beaten Austrians were caught at the Danube, where Servian guns had smashed to pieces a bridge of boats cunningly contrived for retreat. And while they were making their last feeble resistance, a brigade of Servians marched into Belgrade. Flags flew everywhere and the people hailed the return of their own troops deliriously. When the king himself rode in, disdaining the carriage that had been provided for his use on account of his age, the city seemed to go mad. The thunder of the guns to the east died away; the Austrians who had been cut off had had enough of fighting and had surrendered. The Servians were the victors.

"It is wonderful! It will surprise the world!" said Dick. "Why, Mr. Hampton said that everyone believed Servia had lost her last chance, and that the country was about to be overrun, like Belgium!"

Dick met General Dushan, Steve's father. And it was the general, his eyes filled with tears of pride over the exploits of his son, who told them of a great honor that awaited them.

"The king has ordered me to bring you both before him," he said. "He has heard of the part you played in the destruction of the Semlin arsenal and he has learned that it was that feat that made the great victory of Schabatz possible. If the Austrians had had ammunition enough to serve their guns, they would have beaten us there."

Dick was embarrassed and timid when he was called upon to stand forth and meet King Peter. But the old man, simple and, democratic, soon put him at his ease. He held out his hand and gripped Dick's, and then he spoke to him in English.

"Servia thanks you, through me, her king," he said. "I wish you to wear this decoration with our gratitude! And I have heard of the mission that brought you to Semlin—so fortunately for us. General Dushan knows my pleasure in that matter."

"Come with me, both of you," said General Dushan. He took them to the citadel, and there, in a little while, Hallo was brought before the general, his hands linked with steel handcuffs.

"Michael Hallo," said General Dushan, sternly, "you have been tried and found guilty, and sentenced to death as a spy and a traitor. But His Majesty has been pleased to grant you a reprieve—on a certain condition. If you will sign an order to Richard Warner upon the State Bank here for the payment of a sum equivalent to two hundred thousand dollars, you will be confined as a political prisoner until the end of the war, and then released. Do you agree?"

There was hate in Hallo's eyes, but he was helpless—and he agreed, to save his life.

"I told you it would be arranged," said Stepan, three days later, when Mr. Denniston, the consul in Semlin, had arranged for the transfer of Dick's money to New York. "And now you are going to Salonica, with an escort to the border—and I am going all the way to Athens to see you off! Think of us sometimes—and when the war is over, I will visit you in New York!"