The founder of Russia's Wagner mercenary force has said his troops now tightening their grip on the Ukrainian city of Bakhmut are being deprived of ammunition and that, if they are forced to retreat, the entire front will collapse. Yevgeny Prigozhin had said on Friday that his units had "practically surrounded Bakhmut," where fighting has intensified in the past week after months of attritional warfare, with Russian forces attacking from three sides. Wagner often appears to operate autonomously from the regular army, or even in competition with it, and in a video published over the weekend, Prigozhin complained that the...