An MSNBC commentator has reportedly left the network to join an international legion fighting on the side of Ukraine as it seeks to repel a Russian invasion.

Malcolm Nance, the former naval intelligence officer who has served as an on-air analyst at the Comcast-owned cable network since 2007, appeared on Monday’s episode of Joy Reid’s nightly show “The ReidOut” wearing military fatigues and combat gear.

Nance also appeared while carrying what appeared to be a Kalashnikov assault rifle.

He told Reid on Monday that he has joined the International Legion of Territorial Defense in Ukraine.

According to Reid, the legion is comprised of 20,000 volunteers from 52 countries who enlisted to help Ukrainian forces fight the Russian military.

“I spent quite a bit of time here in the pre-war period and when the invasion happened, I had friends who were in Donetsk, who were in the Ukrainian army, who were writing to us and telling us, ‘We’re not going to survive tonight. We’ve been hit 500 times’,” Nance told Reid on Monday.

“The more I saw of the war going on the more I thought, I’m done talking. It’s time to take action here,” Nance said.

“About a month ago, I joined the International Legion here in Ukraine and I am here to help this country fight what is essentially a war of extermination.”

Nance added: “This is an existential war, and Russia has brought it to these people and is mass murdering civilians. And there are people here like who me who are going to do something about it.”

Nance, who is the author of several books about counterterrorism and national security, appeared as an analyst on MSNBC’s air as recently as Feb. 28 — days after the start of the Russian invasion of Ukraine.

The Post has reached out to MSNBC seeking comment.