https://firstlook.org/theintercept/2015/02/26/midst-war-ukraine-becomes-gateway-europe-jihad/
That debt is to Ukrainians like Oleksandr Muzychko, who became one of the brothers, even though he never converted to Islam. Muzyczko, along with other Ukrainian volunteers, joined Chechen fighters and took part in the first Chechen war against Russia. He commanded a branch of Ukrainian volunteers, called “Viking,” which fought under famed Chechen militant leader Shamil Basayev. Muzychko died last year in Ukraine under mysterious circumstances.