Bermontians were Russian troops who were at first taken as POWs by Germany in World War I and then released on the promise that they would help fighting against the communists in the Russian civil war. Instead, led by Pavel Bermont-Avalov , they decided to attack the newly-independent states of Lithuania and Latvia, to which Germany had granted independence.

Bermont thought that in the Russian civil war the communists would be crushed anyway, so there was no need to help fighting against them; instead he thought he could annex the Baltic states, and, once the communists were destroyed, join them to Russia, getting some high position or local ruler's title in exchange. Bermontians managed to take considerable territories in western Lithuania.

Bermontians, once they would annex a town, would ban the local languages there and enforce the Russian language; this and other reasons made them very unpopular with the local population. In Latvia, they managed to take the capital Riga; however the temporary capital of Lithuania, Kaunas, was farther away. Despite having to fight the communists at the same time in the east, Lithuania collected enough forces and started to win territories back from the Bermontians. The Bermontians were finally crushed near Radviliškis , a major railway centre, where they were put into trains and sent to Russia. As for Latvia, Estonia helped it to reconquer lost territories, according to some explanations, in exchange for Latvia ceding the island of Ruhnu and its territorial waters to Estonia.