The image of Vitali Klitschko, bullhorn in hand, mayhem all around him, is unforgettable. In November and December 2013, the Hall of Fame boxer had just ended his career, and was leading what became known as the Euromaidan protests in Kyiv, Ukraine.

A partially burned bus, its windows broken, sits still behind him, evidence of the danger in the streets.

As Klitschko begins to speak into the microphone, a man steps up with a fire extinguisher and sprays him in the face. Klitschko briefly disappears behind the cloud of white.

Seconds later after security pushes him out of danger, he emerges, an angry look on his face. His face is covered with soot, as if someone had thrown a handful of flour on him.

For those who knew and admired Klitschko during his epic run as one of boxing’s great heavyweights, it was a frightening, worrisome time.

Yet, more than eight years years later, those protests seem mild compared to what Klitschko faces today. Russia invaded Ukraine and attacked it on Thursday, starting a war.

Vitali Klitschko never has run from a fight before, and isn’t about to now. This one, though, is one that may well kill him.

He is the mayor of Kyiv, but he’s become the leader of Ukraine’s defensive efforts against Russia. Ukraine President Volodymyr Zelenskyy, a one-time stand-up comedian, spent the past several weeks condemning Russia’s military building up and asking for a diplomatic solution. He accomplished little to nothing.

Klitschko has made it clear he wants peace. The difference in him with most is that he’s willing to do whatever it takes to ensure that peace.

Klitschko is going to lead out front. Asked Thursday by "Good Morning Britain" if he’d take up arms and fight himself, Klitschko never hesitated.

“I don’t have another choice,” he said. “I have to do that.”

He does have another choice. He could work with other political leaders in Ukraine to develop strategies and to seek assistance from NATO and other allies.

He’s a brilliant man with the courage to match his fearsome size and strength, and he knows how important he is to his fellow citizens.

But once a fighter, always a fighter. Klitschko, who was born in the former Soviet Union, believes Ukraine should be free and independent. He believes it would help the country economically and culturally to become part of the European Union.

If Ukraine joins the EU and prospers, it’s likely going to make several other former Soviet states follow suit. Russian President Vladimir Putin, who organized and launched the attack on Ukraine, does not want that.

“Our eastern neighbor is not happy with our decision to become part of the European family,” Klitschko told the U.K.'s Channel 4 News last month. “We do not want to return to the USSR. We were in the USSR and we see our future as part of a European family. Mr. Putin disagrees. They have an idea to rebuild the Soviet Union, but we do not want to return to the USSR. We see our future as a free democracy.

“As a former officer, I spent a lot of time in the army. As a former soldier, I am ready to defend my country, to defend the independence and territorial integrity of Ukraine. Will I fight in the war against Russia? Yes, of course. I will fight in the front lines.”

Where are Russian forces surrounding Ukraine? Check out this explainer from Yahoo Immersive to find out.

A leader on the front lines in a war zone is almost unthinkable in today’s world. But that decision to risk everything to rally his fellow citizens and defend his country’s sovereignty has had to make him a primary target of Putin and may mean he signed his own death warrant.

As an athlete, Klitschko has shown boundless courage in the face of extreme adversity throughout his career. He showed that in a boxing ring in 2003 when he fought Lennox Lewis in Los Angeles and suffered a gaping wound over his eye. He wanted to continue and protested vehemently when the referee decided the cut was too severe.

But that was nothing in comparison to what he’s doing now. He and his younger brother, Wladimir, who joined the Ukrainian Army reserves and will fight shoulder-to-shoulder with him, will be more remembered for what they’ve done in these days than for all the glory they ever attained in boxing.

So many of Putin’s critics have died since he assumed office that a leading Russian scholar, Amy Knight, wrote a book that was published in 2017 called, “Orders to Kill: The Putin Regime and Political Murder.”

The Klitschko brothers know this, and they know that as outspoken critics of Russia in general and of Putin in particular, they could be among the next of his detractors who Putin looks to silence.

There is an immense amount of bravery required to slip between the ropes and fight another man who has trained for months to defeat you. It’s child’s play compared to the fight the Klitschkos face today.

They’ve never backed down from a challenge previously and, sadly, they’re not backing down this time.

Even if the end is near for them, they’re heading into battle full of heart and determination.

It’s all they know.