Private First Class Donald Kowalski was a soldier for the New California Republic Army.
Donald Kowalski fought, and died, at the battle of Hoover Dam. He sacrificed himself so wounded soldiers could be evacuated and was killed when Boulder City was blown up as a trap for Caesar's Legion. He is the older brother of Private Kowalski who can be found "paying his respects" at the memorial in Boulder City.
Donald Kowalski is mentioned only in Fallout: New Vegas.