"Ukrainian volunteers fighting the Soviets"

That's not the only thing they were doing. [0]

"like Azov Brigade"

I'd recommend a book by a Canadian journalist collaborating with Bellingcat on the subject of Azov and other Ukrainian nationalists. [1]

[0] https://en.m.wikipedia.org/wiki/14th_Waffen_Grenadier_Divisi...

[1] http://cup.columbia.edu/book/from-the-fires-of-war/978383821...