A US veteran joined Ukraine's International Legion, then made a shock defection to Russia. Ex-comrades say he was incompetent and left behind a trail of chaos.

• A US veteran went to fight in Ukraine but has defected to Russia.
• Those who fought with him in Ukraine told Insider he was unstable and erratic on the battlefield.
• His time in Ukraine calls into question the vetting processes of the country's International Legion.

When Russia invaded Ukraine in February last year, scores of foreign fighters flocked to help defend the country.

Among them was John McIntyre, a 25-year-old American veteran nicknamed Johnny Alabama, or Bama, by his fellow fighters who took up arms and joined the International Legion of Territorial Defense of Ukraine.

Videos show the American among the uniformed fighters on the ground calling out, "God bless Ukraine," and, "Fuck you, Russia."