In mid-1919, the dissatisfied had an opportunity to mount a serious challenge to Trotsky's leadership: the Red Army grew from 800,000 to 3,000,000 and fought simultaneously on sixteen fronts. The Red Army had defeated the White Army's spring offensive in the east. It was about to cross the Ural Mountains and enter Siberia in pursuit of Admiral Alexander Kolchak's forces. But in the south, General Anton Denikin's White Russian forces advanced, and the situation deteriorated rapidly. On 6 June, Red Army commander-in-chief, Jukums Vācietis, ordered the Eastern Front to stop the offensive so that he could use its forces in the south. But the leadership of the Eastern Front, including its commander Sergey Kamenev (a former colonel of the Imperial army), and Eastern Front Revolutionary Military Council members Ivar Smilga, Mikhail Lashevich and Sergey Gusev vigorously protested and wanted to keep the emphasis on the Eastern Front. They insisted that it was vital to capture Siberia before the onset of winter and that once Kolchak's forces were broken, many more divisions would be freed up for the Southern Front. Trotsky, who had earlier had conflicts with the leadership of the Eastern Front, including a temporary removal of Kamenev in May 1919, supported Vācietis.