Canadian fans booed the American national anthem when the teams met in a round-robin match in Montreal, which was followed by three fights in the first nine seconds of the game.

The U.S. and Canada men’s ice hockey teams, set to play in the 4 Nations Face-Off tournament final on Thursday night, have come to represent more than just their athletic skill. On both sides of the border, the rivalry in the rink has been seen by some as an extension of the political tensions between the once-friendly allies.

The 4 Nations Face-Off Final between Canada and USA, a thrilling contest won by the Canadians in overtime, was a massive boon for the sport of hockey and its viewership.