On the morning of July 29, 1914, the day after war had been declared, the residents of Belgrade were startled by a deep roar, followed by the whistling shriek of a huge body, hurtling through the air, and a shell burst over the battlements of the old Turkish citadel, doing no damage. Immediately there came another deep shock; the Serbian guns were responding. Thence on the cannonading along the Danube front continued for week after week, with only now and then a lull. The Austrian batteries bombarded not only Belgrade, but Semendria, Gradishte and a number of other points along the river bank. Next they were seen building a pontoon bridge out to one of the little islands in the river, opposite the city and barges were towed alongside the landings on the opposite shore, presently to be crowded with black masses of Austrian troops. Naturally, the Serbian gunners made these objects the targets of their fire. But these were mere bluffs, such feints as the skilled boxer makes when he wants to get behind the guard of his opponent. If anything, these demonstrations only served to deepen the conviction of General Putnik that the real danger was not from this quarter. But where was the first great blow to strike? Naturally, not only the General Staff, but the whole army and population waited in deep anxiety. This tension lasted over the last days of July, into the first week of August, 1914. Then, on August 6, 1914, some Bosnian peasants, Serbs, appeared and reported that they had seen great bodies of soldiers moving along the mountain roads toward Syrmia, in northeastern Bosnia. Two days later, early in the morning, two Austrian aeroplanes whirred over the River Save and circled over Krupanie, Shabatz and Valievo. The last doubts were then dispelled; the attack was coming from the east. And finally, on August 12, 1914, the message flashed over the wires that the outposts had seen boats in movement, full of soldiers, behind an island on the Drina, opposite Loznitza. Near that town, and in fact along the whole lower course of the Drina, the river has frequently changed its channel, thus cutting out numerous small islands, which would serve as a screen to the movements of troops contemplating a crossing. Pontoon bridges could be built on the farther side of almost any of these islands without being observed from the other shore. This was exactly what the Austrians were doing. [Illustration: Serbian Infantrymen on Their Way to the Front.]