Write a question about the following article: At the beginning of March 1919 the general offensive of the Whites on the eastern front began. Ufa was retaken on 13 March; by mid-April, the White Army stopped at the Glazov-Chistopol-Bugulma-Buguruslan-Sharlyk line. Reds started their counteroffensive against Kolchak's forces at the end of April. The Red 5th Army, led by the capable commander Tukhachevsky, captured Elabuga on 26 May, Sarapul on 2 June and Izevsk on the 7th and continued to push forward. Both sides had victories and losses, but by the middle of summer the Red Army was larger than the White Army and had managed to recapture territory previously lost. Following the abortive offensive at Chelyabinsk, the White armies withdrew beyond the Tobol. In September 1919 a White offensive was launched against the Tobol front, the last attempt to change the course of events. However, on 14 October the Reds counterattacked, and thus began the uninterrupted retreat of the Whites to the east. On 14 November 1919 the Red Army captured Omsk. Adm. Kolchak lost control of his government shortly after this defeat; White Army forces in Siberia essentially ceased to exist by December. Retreat of the eastern front by White armies lasted three months, until mid-February 1920, when the survivors, after crossing Lake Baikal, reached Chita area and joined Ataman Semenov's forces.
About how long was it before the Reds' counteroffensive began?