Two-time Academy Award winner Sean Penn was with Ukrainian President Volodymyr Zelenskyy when Russia invaded Ukraine — as he filmed a documentary that was intended to be about a comedy superstar-turned-president but ended up being about an existential threat to democracy. 

Penn said Zelenskyy changed that day in February last year, and he noticed the shift when the two were together in the bunker of the presidential palace during the start of the invasion.

"I met him the day before and .. when he entered the room on the day of the invasion, to our cameras, ... it felt like he was born for this .. and it was a seamless rise," Penn told "CBS Mornings" on Wednesday. "It was a different person, cellularly, than the one I had met the day before. And he had —  and has — as the Ukrainian people do, just complete resolve."

Their meeting is documented in the new film "Superpower," about the Ukraine war. Penn said it started as a "light-hearted tale" about Zelenskyy and that he met with the president over Zoom "long before the drums were beating on the Russian invasion." 

The COVID-19 pandemic delayed the start of filming, and their first in-person meeting didn't take place until Feb. 23 last year, the day before the full-scale assault. They agreed that afternoon to start filming on Feb. 24 — a commitment Zelenskyy kept despite the unfolding crisis. 

"I think that he understands that part of war-fighting in the new world is communications on a lot of levels," Penn said about why Zelenskyy agreed to film under the circumstances. "I think that what he felt was that there was going to be a time when tools like this, communications tools, would be part of the war-fighting effort."

Penn made seven trips to Ukraine for the film, which premieres on Paramount+ on Monday, Sept. 18. While there, he said he "finally" felt the unity and community Americans were promised in their own democracy.

"What you have in Ukraine is the most civil democracy, the tightest community, the greatest unity of any place I've ever felt in the world, and it's a direct representation of the best of the aspiration that we call our democracy," he said. 

He said he hopes the film gives "context to Americans around the kitchen table to understand the ways in which everything that happens in Ukraine will be on our table, and that it's not so simple as to say, 'Oh, we're putting money in another country.' No, it's a great investment in our future."  

If Americans don't support Ukrainians in their fight, Penn said, "we're gonna lose a lot."

In:
• Ukraine
• Russia