KYIV -- The average lifespan on the frontline of the fierce fighting in the city of Bakhmut is "four hours," according to an American fighting side by side with the Ukrainian army against Russian forces in the Donbas. Former U.S. Marine Troy Offenbecker, of Michigan, told ABC News that the situation in the city, which has seen some of the deadliest fighting since Russia's full-scale invasion, is "chaotic" and has been dubbed "the meat grinder." "It's been pretty bad on the ground," he told ABC News. "A lot of casualties. The life expectancy is around four hours on the frontline."