One of the events in the novel Commissar is the Allied intervention in Russia. Overshadowed by World War I, this is an often-forgotten episode in world history which influenced the Soviets’ relations with the West for decades after the war.
In the summer of 1918, a coalition of WWI allies deployed troops to Russia’s Far East, to oppose the Bolshevik regime and support the White armies in the Russian Civil War. (Another allied force was deployed at the same time in Russia’s North in Arkhangelsk.)
The buildup in Siberia began in the port city of Vladivostok with just several thousand British, American, Canadian and Japanese troops. Over the following years, the allied force grew to over 140 thousand, with almost 70 thousand Japanese, 50 thousand Czechoslovaks, 8 thousand Americans, 4 thousand Canadians, and thousands more of French, Belgian, Italian, Polish and Chinese troops.

Pictured here are senior commanders of the Japanese, American, British, Italian and Belgian forces.
(Yes — that does appear to be the skin of a Siberian tiger under the boots of the Japanese General Kikuzo Otani)
The allied troops engaged in military action against the Red armies throughout Siberia and as far east as the city of Omsk, where they supported the White government of Alexander Kolchak.

The intervention lasted through much of the Russian Civil War, although in the Allies’ home countries public support for continued engagement declined steadily after the end of WWI. Most of the allies withdrew in 1920, with only the Japanese remaining until the end of the Russian Civil War in 1922.
* images: US Public Domain, IWM Non-Commercial Licence