Russia building a massive airforce then sinking the home fleet of Japan(mostly) allowing the USA to pretty much walk into the Japan and take it. Btw…Russia didn’t share this plan with the other allies they just did it lol.
They were not intentionally cheating, I am sure, however, they are still breaking the rules and will have to be penalized accordingly. Which probably means returning their ships to the proper sea zones, removing the infantry and surrendering whatever collected money they had to the bank.