WASHINGTON — When Matthew Parker, an American veteran with 22 years of service in the U.S. Army, heard that Russian forces had invaded Ukraine, he thought about a Ukrainian American soldier who had served alongside him with U.S. forces in Iraq and decided he wanted to help the Ukrainians defend their homeland.

“I had a soldier in Iraq with me who was from Ukraine,” he told VOA of his decision to join what he sees as a fight about justice and friendship. “He became an American citizen, joined the Army, and he told me about his home. He told me about his family and how proud they were. I remember him telling me about his little sister.

“Now … I’d like to think that by going to Ukraine, maybe I protect his mother, or his little sister or his home. Maybe in some small way, I say thank you to him for serving by doing something like this.”

Parker, who fought battles in Bosnia and Iraq, is not alone.

A representative of the Ukrainian Embassy in Washington told VOA that 3,000 U.S. volunteers have responded to the nation’s appeal for people to serve in an international battalion that will help resist Russia’s invading forces. Many more have stepped forward from other countries, most from other post-Soviet states such as Georgia and Belarus.

In an emotional video posted to his Telegram channel on Thursday, Ukrainian President Volodymyr Zelenskyy referred to an “international legion” of 16,000 foreign volunteers, who he said are being asked to “join the defense of Ukraine, Europe and the world.”

“We have nothing to lose but our own freedom,” the president said.

Zelenskyy’s appeal was echoed in a Facebook posting by Ukraine’s armed forces, which emphasized they are looking for people with combat experience who “are standing with Ukraine against [the] Russian invasion.” The government has already temporarily lifted visa requirements for the volunteers.

For Parker, a gray-haired father with four adult children, the decision to go and fight in Ukraine came even before Zelenskyy’s appeal.

Initially, he and 12 veterans, men he served with over the years, planned to board a plane to Poland, get to the Ukrainian border and register for territorial defense units along with other Ukrainian volunteers.

The path forward became much clearer, however, after Zelenskyy called for the formation of the international legion and the Ukrainian government laid out a procedure for people who want to help.

“When we did not have the procedure, it would have been a process of showing up at the border. Maybe not knowing how to speak the language and trying to convince somebody. This way, they know our experience. They know our training. They can send us to places where they need us,” he said.

Parker, a native of the U.S. state of South Carolina, said in his years with the U.S. Army, he had been an instructor as well as a combat leader who led soldiers in combat situations.

“They can place me where they need me,” he said. “Or they can only leave me as an instructor with the legion to teach Ukrainians how to use different weapons systems. So now they have a choice, they can put me in combat or use me as an instructor, but we’re happy to help in whatever.”

For Parker, the fight in Ukraine is about more than the defense of one central European country that has been subjected to an unprovoked attack by a larger neighbor. Like many of the volunteers, he feels that Americans’ own democratic rights will be threatened if Russia is able to prevail.

“What Ukrainians are fighting is a bully, they are facing someone who does not honor international law, who does not care about women and children, and we fought this type of people before,” Parker said.

“We’re stopping a bully from hurting women and children.”

Another of Parker’s former combat friends was from Georgia, where Russia staged a similar war in 2008.

“They served next to me, soldiers from Georgia in Iraq. And I know how it felt being around them while their country was being attacked. Now we have another free country similar to Georgia that’s being attacked,” he said.

Parker said he is leaving his security training business in South Carolina, his family, and three dogs and heading to Ukraine as soon as next week.

Russian President Vladimir Putin “has already taken the Crimea,” he said. “Which should have never been allowed. That was a weakness by the international body. He can’t be allowed to take the rest of Ukraine.”