Between Obrenovatz and Kratinska, on the Save, the Austro-Germans had delivered heavy attacks for three nights successively, but were effectively checked. The operations were directed specially against Zabrez. On October 10, 1915, this Serbian position was still holding out. In the afternoon of that date the Austrians bombarded heavily, using great quantities of asphyxiating bombs. Then they charged in solid masses, believing that the gases had thrown the Serbians into disorder. The latter, however, were provided with masks, and when the enemy charged they sprang from their trenches and met them on the open ground in hand-to-hand bayonet fighting, driving them back in panic. Again the Austrians showered gas shells on the Serbians; then, toward dusk, came on again, but the Serbians once more broke through the Austrian ranks and captured many prisoners. [Illustration: The Beginning of the German-Austro-Bulgar Campaign against Serbia.] But in spite of these local successes by the Serbians, the fighting was beginning to go against them; the invaders had crossed the frontier and could no longer be dislodged. On October 11, 1915, the official German dispatches were able to announce that Mackensen's forces were in possession of the Serbian banks of the Danube and the Save between Gradishte and Shabatz, a stretch of over a hundred miles. On the Drina too, the Austrians had been able to cross over in several places. To all these points they hurried large bodies of reserves to push their advantages and so continue a vigorous offensive east, south, and west of Belgrade, in a wide, sweeping movement along the entire front. The main effort was made in the east, to secure possession of the Morava Valley and its railroad. Near Semendria, Gallwitz's right wing was in touch with Koevess's left. The plan was that they should advance up the Morava together, each covering one side of the valley. But it was first necessary to reduce the Serbian forts at Semendria and Pojarevatz. It was now two weeks since the heavy artillery had begun playing on Semendria. By October 11, 1915, the invaders had succeeded in taking Semendria, the garrison retiring to Pojarevatz. Here a very severe battle was fought, but finally the Serbians were forced back, though not without inflicting the heaviest losses that the enemy had as yet suffered. After two days the fort was taken and the Serbians retired to the hills beyond. Thus the invaders were now ready to begin their advance down the Morava Valley. But just then there came a pause in the fighting. The Serbians observed that Gallwitz waited. What he waited for was not immediately obvious to them. Within a few days they were to know. CHAPTER XXXII BULGARIA ENTERS THE WAR