Henry, there are two different groups of Russians.
After the RCW, large numbers of Russians left to China, and some of them stayed as units intent on returning to recapture Russia. In Sinkiang there was Annenkov and Bakich, which are the ones posted in this thread. There were also some in Mongolia, notably the Mad Baron. They had local auxiliaries, since at that time the border wasn't yet fixed for such people.
Those units were suppressed in the years following 1920. Some of the units were destroyed when they attempted an invasion of Russia themselves, the rest when the Soviets actually invaded China a couple of times to do so.
Those units kept Russian uniforms, as much as they could.
Meanwhile individual Russians fleeing the Soviets found employment as individuals in the various Chinese armies. Those are the "White Russians in China" of Copplestone.
adds an infantry platoon to his WWI Brits.
