Mercenaries from 40 countries fighting against Russia

Or, for Ukraine, if you prefer

“The overwhelming majority of them are Poles, of which there are 5,000, Rogov specified. He also said Japanese, Australian, Canadian, French nationals and people from Spanish-speaking countries among mercenaries.

“Rogov also recalled that more than a thousand mercenaries had already been killed in the city of Zaporozhye.”

https://tass.com/russia/1535673

Poland and the USSR fought a brutal war for two years, 1919-21, following the Bolshevik overthrow of the Kerensky government, with Poland planning to take back western Ukraine, which once before had been part of Poland. Plus, Russia occupied Poland for more than 100 years, 1815-1918, as agreed by the major European powers. As with the Balkans, no love lost between neighboring countries.