The US send 4 regiments, all infantry, to guard military stores at Murmansk and Vladivostok, armed with Mosin-Nagent rifles (manufactured by Remington for the Tsar). There was concern that German forces would be able to capture the materiel, and with the Bolshies signing a treaty with the Germans, use the materiel against the Allies.
The two regiments near Murmansk were sent south, and gained a great deal of space. Their commanders took instruction from the British official on the scene, to their shame. They set up a network of interlocked fortifications that were very effective against the Red Army.
The two regiments near Vladivostok secured and operated the Trans-Siberian railroad. The Czech Legion was one unit that was able to escape from Soviet Russia.
Made this thread well worth it.