The fall of Lemberg was followed by the loss of the Dniester line as far as Halicz, and all beyond it including the Bukovina, and the Russians fell back behind the Gnilia Lipa, where Ivanov prolonged a stubborn resistance. But the aims of the Germans in Galicia had been achieved with the capture of Lemberg except in so far as the remnants of the Russian armies remained intact. The city formed a formidable bastion for defence because of its ample lines of communication with the south and west, and inadequate lines to the north and east. A farther German advance across the Russian frontier in that direction would be an eccentric movement, and the front of attack was accordingly swung round from east to north, where the Russian position in Poland had been outflanked. The reconquest of Galicia produced fruits enough in the restoration of Austrian and Hungarian confidence and the repression of pro-Entente tendencies in the Balkans. But it was only a part of the most ambitious and successful campaign the Germans fought in the war. May and June were but the prelude to greater successes in July, August, and September. The heaviest blows were to be struck in the Polish centre, but diversions had already been made on the extreme German left in the north. Libau had fallen on 9 May, and during that and the following month the German armies under Von Buelow overran the duchy of Courland as far as Windau on the coast and Shavli half-way to Riga. This movement was regarded with comparative indifference as being a divergent operation calculated at worst to do no more than distract Russian forces from more critical points. But it was in keeping with a German design considered grandiose until it nearly succeeded. The bulk of Russia's forces were concentrated in the Polish triangle of which the apex was at Warsaw, the base ran from Kovno by Brest-Litovsk to the Galician frontier, the north-western side in front of the railway from Kovno to Warsaw, and the southern in front of that from Warsaw to Lublin, Cholm, Kovel, Rovno, and Kiev. The German plan was not merely to squeeze the Russians out of the triangle by pressure on the sides and intercept as much of their forces as possible, but also to outflank the whole position by striking behind the base from the north at Vilna; and a naval attack on Riga was part of the projected operations.