Donald Hallen was born in Toronto from a Canadian father and an American mother. He and his mother moved to Wisconsin in the USA when he was still a toddler, and he obtained US citizenship, even before going to school.
Captain Hallen could be considered the opposite of Lieutenant Clarke. He joined the US Army only as a way to get rich quickly, through some dark dealings in war zones. After a series of scandals on peace missions in Afghanistan, Somalia and Sudan, and although his participation couldn’t be proved, it was strongly suggested to him that he leave the military. He continued his career as a soldier of fortune and after fighting in the Balkans war he created his own mercenary team that was discovered and hired by Mr. Goldenberg.
He's cruel and cunning, but not particularly smart. He based his efficiency being stubborn and direct. If he has some virtue, it will be his concern and loyalty to his team mates. He's also fearless, almost bordering on the daredevil concept. Usually, he would weigh up his acts in order to avoid risky situations.