Ethan Scheiner of the Washington Post explains
On Feb. 15, 1968, the hockey team of Czechoslovakia, of which Slovakia was part, took on the Soviet Union at the Olympics in Grenoble, France. Czechoslovakia’s challenge extended far beyond the ice: The game served as a lightning rod in the movement for political freedom back home, a role hockey would continue to play in the country for the next two decades.
Then came the “Prague Spring.” In 1968 a new Czechoslovak government took power. It instantly asserted greater independence from Moscow and instituted reforms that permitted greater freedom of expression, travel and the press. Because many Czechoslovaks believed (inaccurately) that Moscow’s control had prevented them from defeating the Soviet hockey team, they looked to a victory over the USSR for proof that the reforms were genuine and far-reaching.
When the two squads faced off in the 1968 Olympics, the Soviets had won the past five world titles, were unbeaten in their previous 38 world championship games and had defeated Czechoslovakia in every major tournament since 1961. But this time, in a stunning upset, Czechoslovakia won 5-4. In the game’s iconic moment, Czechoslovakia’s melodramatic team captain Jozef Golonka dove onto the ice to celebrate, leading to hockey folklore that he was trying to hear if Russia had cut off oil to Czechoslovakia as punishment.
Although the Soviets went on to take the gold medal, for Czechoslovaks the win over the Russians catalyzed a new sense of possibility. Tens of thousands of fans took to the streets to celebrate the team.
It's a pretty fascinating article about hockey played a key role in a country keeping it's identity in the face of oppression. Here's the full story.