The winter battles of the Mazurian Lakes had forced the armies at the northern end of the Russian right flank back into their great fortresses Kovno and Grodno, and behind the line of the Niemen and the Bobr. A great forest region lies to the east and north of Grodno, and between the Niemen and the cities of Augustowo and Suwalki which the Germans, after their successful offensive, used as bases for their operations. A strip of country including these forests, and running parallel to the Niemen was a sort of no-man's land in the spring of 1915. Movements of troops in the heavily wooded country were difficult to observe, and the conditions lent themselves to surprise attacks. This resulted in a warfare of alternate thrusts by Russians and Germans aimed now at this point, now at that, in the disputed territory. Several actions during the spring stand out beyond the rest in importance, both because of the numbers engaged and their effects. In what follows will be described a typical offensive movement in this district undertaken by the Russians, and the way it was met by the Germans. A new Russian Tenth Army had been organized by the end of February, 1915, with Grodno for its base. General Sievers, his chief of staff, and the general in command of the Third Russian Army Corps had been demoted from their commands, and three new army corps (Two, Three, and Fifteen) had been brought to Grodno. The ranks of the remaining corps that had suffered in the "winter battle" had been filled up with fresh recruits. Hardly had the German pursuit in the forest of Augustowo come to an end when the freshly strengthened Russians moved forward from their defensive lines in a counterattack. The Germans had been engaged in the task of gathering and carting away their enormous booty which lay scattered about the forest. They now drew back from in front of the Russian fortified lines to prepare positions close to Augustowo, and on a line running roughly north and south from this place, with the forest in front of them. The Third Russian Army Corps advanced from Simno toward Lozdsisjo, their Second Army Corps from Grodno by way of Kopiewo and Sejny toward Krasnopol and other Russian corps advanced through the forest of Augustowo. Here they soon struck strong German resistance, and for several days vainly attacked German fortified positions.