Former heavyweight titlists Wladimir and Vitali Klitschko have no plans on ducking from possibly the largest military conflict on European soil since the end of World War II.

On early Thursday morning, Russia launched a full-scale invasion of its neighbor in Ukraine, the Klitschko brothers’ homeland, with an initial attack that included roughly 100 missiles fired from land and sea, according to a senior US official. Thus far more than 50 Ukrainians have died in the conflict. The attack has drawn broad international condemnation.

The Klitschko brothers, who dominated the heavyweight scene throughout the 2000s and remain today among the most recognizable denizens of Ukraine, made various efforts Thursday to muster up public support for their country’s cause.

In a Linkedin post titled “No Democracy without democrats”, Wladimir Klitschko pleaded with the world to protest Russia’s belligerent encroachment on his nation’s sovereignty, while taking special aim at what he calls Russian president Vladimir Putin’s “megalomania.”

"You can do something by mobilizing and organizing huge demonstrations,” Wladimir wrote. “Make your voice heard. Make the voice of democracy heard. Say it loud and clear that international law and democracy are under attack, that war is the greatest evil and that life is sacred. Also say that while solidarity is good, support is better. Say that the march of imperialism must be stopped now. After all, whose turn will it be after Ukraine?

“This war against my country is not only the result of one man's madness, but also the result of years of weakness in Western democracies. This madness must be stopped now by stepping up deterrents.”

Vitali, the older brother of Wladimir and current mayor of Kyiv, the capital of Ukraine, promised he would take up arms to help fend off the Russian onslaught.

“I don’t have another choice,” Vitali told Good Morning Britain in response to a query if he plans to stand down and fight. “I have to do that.

The elder Klitschko has been involved in Ukrainian politics since 2005. He has held the mayoral office since 2014 and is currently in his third term.

The brothers later appeared jointly in a video in which Wladimir stressed solidarity with Ukraine, as Vitali grimly looked on.

“To observe this tragedy that is happening nowadays in Ukraine, in this senseless war, is not going to have any winners but losers,” Klitschko said. “I just want to tell you we must stay united at least against this Russian aggression. Don’t let it happen in Ukraine, don’t let it happen in Europe, and eventually the world. United we’re strong. Support Ukraine, thank you.”

Wladimir Klitschko (64-5, 53 KOs) retired in 2017, upon a knockout loss to Anthony Joshua. Vitali Klitschko retired for good in 2012 after beating Mahmoud Charr by fourth-round knockout.