Once more the Russian advance in Galicia was resumed. (Vol. III, 264.) Russian armies never again approached Cracow, but they did come to the Dunajec line, while to the south they began the slow ascent of the Carpathians (Vol. III, 261-264), across which raiding forces of Cossacks had several times passed. They also concentrated against the fortress of Przemysl, the last Austrian stronghold along the San. This campaign endured throughout the winter. Finally Przemysl, with a garrison of 125,000 men, surrendered in early March (Vol. III, 249-257), and Russia was at last free to strike either at Cracow or through the Carpathians for the Hungarian Plain.
Her decision to go south was probably influenced by the great victory of the Serbs at Valievo. While German aid was taking pressure off the Austrians a new Hapsburg thrust had been delivered at Serbia, Austro-Hungarian troops had passed the Drina and penetrated deeply into Serbia, Belgrade had fallen, and the end of Serbia seemed in sight. But new Russian attacks having compelled Austria to recall many of her troops, the remaining Hapsburg forces in Serbia were almost destroyed in the bloody defeat of Valievo in December. (Vol. II, 325-357.)
To offset this the Germans soon won one more great victory in East Prussia, at the Mazurian Lakes, where another Russian army was well-nigh destroyed by the quick-marching, better-trained German troops. And this victory beat down another Russian invasion of East Prussia and, as it turned out, closed the period of immediate peril for the German territories in the east.
In March and April the Galician campaign reached its climax in the bloody battles of the Carpathians and Russian armies seemed slowly but surely pushing their way over the mountains and descending into the Hungarian Plain. (Vol. III, 235-276.) It was at this moment that Italy had chosen to enter the war on the allied side, and there was every reason to believe that Rumania would follow.
Instead there came a sudden and tremendous German victory which was to prove the prelude to more victories and to a summer of unparalleled success for German arms. This victory was won at the Battle of the Dunajec—named Gorlice by the Germans—which may well rank with the Marne as the second great struggle of the war, since it saved Austria, brought Russia to the edge of ruin and wholly transformed the horizons of the conflict. (Vol. III, 264-276.)
It will be recalled that at the outset of the war the German General Staff had to choose between two possible operations, an offensive against France or an offensive against Russia. It had chosen to attack France and had lost the campaign. It had in addition failed measurably in its defensive against Russia and the result had been the loss of most of Galicia with the incidental Austrian disasters.
But the campaign in the west had resulted in the occupation of advantageous positions far within French territory and in the conquest of most of Belgium.
Now the German General Staff was again able to decide whether it would turn its entire energies for the summer of 1915 against France or against Russia. If it chose to attack Russia there was solid reason for believing that neither in munitions nor in numbers would the Allies in the west reach a point where they would become dangerous before autumn and between May and October Germany could hope to put Russia out of the war, particularly as Germany knew what the rest of the world did not, that Russia was at the end of her munitions, and her long and terrible campaigns in Galicia, together with her defeats in East Prussia, had temporarily much reduced the fighting value of her armies.