Sentence:  ...ex-Imperial officers who came to the Don and the <WSD>Kuban</WSD> to take arms against Lenins regime... 
Meaning of the word marked with <WSD> tags:  a river in Russia, in the North Caucasus region. It flows through the Karachay-Cherkessia, Stavropol Krai Krasnodar Krai, and Adygea.