Petr Fiala has powerful early memories of tanks. In August of 1968, the Soviet Army invaded Czechoslovakia and crushed an uprising against the Soviet Union’s dictatorial rule. More than 100 people died in the street while resisting the soldiers.

Back then, Fiala was just 4 years old, but he can still recall his parents’ shock and distress, which lingered long after the Soviet soldiers had withdrawn to their nearby barracks.

Now, Fiala is 57 and prime minister of the Czech Republic, which split peacefully from Slovakia in 1993. The Soviet invasion that went down in history as the “Prague Spring” has left Fiala extremely vigilant when it comes to Russia.

This is why Fiala did not hesitate when the idea of going to war-torn Kyiv to meet Ukrainian President Volodymyr Zelensky came up at the European Union summit in Versailles.

“I saw the Soviet tanks in the streets of Prague and I know very well what it did to my country for the next 20 years. I don’t want to see Russian tanks here or anywhere else in Europe again,” Fiala said in an exclusive interview with The Daily Beast.

“If we don’t beat him [Putin], he will not stop in Ukraine. He will roll on and will recreate the USSR.”

Last week, three NATO prime ministers traveled by train to Kyiv to show support for Zelensky in person. Polish Prime Minister Mateusz Morawiecki and Slovenian Prime Minister Janez Janša joined Fiala on the highly unusual journey into a warzone.

They made it to Kyiv unscathed and were transported in a convoy of cars to a bunker-like facility where Zelensky met them.

He had seen some of Zelensky’s speeches to the European and British parliaments and to the U.S. Congress, and had felt moved. Meeting Zelensky in-person, Fiala saw obvious exhaustion in him, but he also observed rational determination and strategic thinking.

“These qualities of his can be, in the end, decisive and it filled me personally with a great hope,” says Fiala.

He came back to Prague with one urgent priority—weapons delivery to Ukraine, especially anti-tank and anti-aircraft missiles. “If they [Ukranians] have enough of these weapons they can create their own no-fly zone,” said Fiala.

“But they need these weapons not in months, weeks, not tomorrow, they need them now. I think even rich countries did get it. I have seen in the last 10 days a big shift in their thinking. They did send weapons.”

Besides weapons, it is economic sanctions that Fiala and the other leaders from Eastern Europe see as a powerful tool to defy Putin. “I think it was us in the East, our storytelling and historical experience, that ultimately led the whole of Europe to impose the sanctions against Putin’s Russia,” Fiala said.

For a brief moment during the interview, Fiala went further back into history, this time evoking a different era: Sept. 30, 1938. On that day, the Munich Agreement was signed, essentially giving Czechoslovakia away to Adolf Hitler. The Western powers thought this would appease Hitler and prevent war in Europe. They miscalculated.

“We in Eastern Europe tell our allies in Western Europe that we have to stand up against this [Russian] aggression and remind them that in the past we didn’t and it was a disaster,” Fiala continued.

“Putin is a war criminal. We must isolate him, we must isolate the whole of Russia. This is the only way we can win this war. And, I believe Putin will be held accountable for his crimes.”