Two Austro-Hungarian armies, 400,000 strong, under the command of Gen. Potiorek, were secretly concentrating at six points along the Western and Northern Serbian frontiers, 340 miles in extent. On the Western frontier, the River Drina divided Serbia from Bosnia.
On the Northern frontier the natural boundary was formed by the Save River, west of Belgrade, and the Danube River east of Belgrade. Thus the Serbian capital was included in a salient which projected into Austro-Hungarian territory on the northwest.
By simultaneous invasions north and west, the Austrians expected to cut through this salient, capture Belgrade and with it a part of the Serbian army. The Serbian forces, all veteran soldiers who had recently emerged victorious from two Balkan wars, numbered 200,000 rifles. Under the direction of Field Marshal Putnik, they were likewise concentrating near the northern border.
On August 12, 1914 the Austrian batteries on the west bank of the Drina River, opposite the Serbian city of Loznitza, opened a heavy bombardment of the town. Under cover of this fire, a fleet of barges, filled with Austrian soldiers, crossed the river. The landing was opposed by two Serbian battalions, acting as an outpost, supported by a few old field guns. They were quickly driven back to the heights behind Loznitza, where they continued their plucky resistance.
The Austrians then laid a pontoon bridge across the Drina and landed an army of 120,000 on Serbian soil, quickly throwing up defensive breastworks and constructing elaborate trenches.
On the same day an Austrian army, 100,000 strong, crossed the Save River at Shabatz, on the Northern frontier, strongly fortified the town, and laid a pontoon bridge across the river from the railroad terminus at Klenak.
Four other Austrian columns were invading Serbia at Zvornik, Luibovia, Amajlia and Branjevo. All these positions converged on Valievo, the terminus of a railroad, extending into the heart of Serbia.
The two mai...