The armies to the south of this group, cooperating in the drive under Field Marshal von Mackensen which had gained the Teutons Przemysl and Lemberg, had as their left flank the forces of Generals von Woyrsch and Koevess between the Pilica and the Vistula mouth of the San. The troops of Archduke Joseph Ferdinand were pushing forward on the right of these, and the army directly under Mackensen himself came next in line to the eastward, joining up with the armies still operating in Galicia at the extreme right of the great German battle line. The chief danger to the Russians at this stage still threatened from the south, where the archduke and Mackensen had pushed forward irresistibly in their advance to the east of the Vistula toward the railway running from Warsaw through Ivangorod, Lublin, Cholm, and Kovell to Kiev and Moscow. The advance of these Austro-German armies, which had operated in the neighborhood of Lemberg, was extremely rapid in the last days of June, 1915. In four days they covered from thirty to forty miles in pursuit of the Russians. By the 1st of July, having swept out of Galicia, their right, under Mackensen, entered the upper valley of the Wieprz, a marshy country which presented considerable difficulty to the advance of troops where a tributary of the Wieprz, the Por, afforded the Russians a natural line of defense. Drasnik, on the Wyznica, which here extended the Russian defensive line westward, was occupied by the archduke's forces on Mackensen's left on the 1st of July, 1915. The drive of the Austro-German armies through Galicia has been dealt with in the account of the Austro-Russian campaign. As we carry forward the account of the activities of the greatest part of the forces concerned in that series of operations from the point where they crossed over the boundary between Galicia and Poland out of Austrian territory, it will be well to glance backward a moment to enumerate here briefly the gains of these armies on Polish soil up to the 1st of July.