During this period there was considerable activity in East Prussia, and the Courland coast was bombarded by the German Baltic squadron. There was every indication that Austria was near collapse, but all the time the Germans were preparing for a mighty effort, and the secret was kept with extraordinary success. The little conflicts in the Carpathians and in East Prussia were meant to deceive, while a great army, with an enormous number of guns of every caliber, and masses of ammunition, were being gathered. The Russian commanders were completely deceived. There had been no change in the generals in command except that General Ruzsky, on account of illness, was succeeded by General Alexeiev. The new German army was put under the charge of von Hindenburg's former lieutenant, General von Mackensen. This was probably the strongest army that Germany ever gathered, and could not have numbered less than two millions of men, with nearly two thousand pieces in its heavy batteries.
On April 28th, the action began. The Austro-German army lay along the left of the Donajetz River to its junction with the Biala, and along the Biala to the Carpathian Mountains. Von Mackensen's right moved in the direction of Gorlice. General Dmitrieff was compelled to weaken his front to protect Gorlice and then, on Saturday, the 1st of May, the great attack began. Under cover of artillery fire such as had never been seen before bridges were pushed across the Biala and Ciezkowice was taken. The Russian positions were blown out of existence. The Russian armies did what they could but their defense collapsed and they were soon in full retreat.
The German armies advanced steadily, and though the Russians made a brave stand at many places they could do nothing. On the Wisloka they hung on for five days, but they were attempting an impossibility. From that time on each day marked a new German victory, and in spite of the most desperate fighting the Russians were forced back until, on the 11th, the bulk of their line lay just west of the lower San as far as Przemysl and then south to the upper Dniester. The armies were in retreat, but were not routed. In a fortnight the army of Dmitrieff had fallen back eighty-five miles.