The Eastern Front counteroffensive was a Bolshevik offensive operation of the Russian Civil War which occurred in the Ural and Volga regions of eastern Russia from April to July 1919. After the successful spring offensive of the White Army in early 1919, which achieved a breakthrough in the center of the Red Army's Eastern Front, the Red Army launched an offensive of its own on its southern flank. The Reds aimed to crush the dispersed White groups one by one, rebuilding the 5th Army from reserves to delay the Whites' advance. During the Red counteroffensive, the Whites failed to capture Orenburg from 22 to 25 April, and the remnants of the defeated White Army defected to the Reds. On 25 April, the Supreme Command of the Red Army's Eastern Front ordered an advance, and, on 28 April, the Reds crushed 2 White divisions southeast of Buguruslan, which fell on 2 May 1919. The Whites grouped 6 regiments near Ufa and planned to outflank the Red Army's Turkestan army, and the Whites were crushed on 29 May, a day after crossing the Belaya River. On 7 June, the Reds captured Birsk (in Bashkortostan), and, on 16 June, the Whites began a general retreat. The Red Army was enabled to cross the Ural mountains by their victory, and the Siberian Army was forced to retreat before the Reds could cut its communications.