Harlan was a training commander in the Last Great Time War. He was one of the most experienced trainers and was tasked by the War Ollistra to train the Eighth Doctor.
After the Doctor started a food fight, he placed the Doctor in solitary. He admitted to the Doctor when the Daleks attacked the Time Lord training facility that his highly-militaristic attitude was for the benefit of raising morale in the recruits and respected the Doctor's methods from before the wartime, calling him a "hero of the old Gallifrey".
Nevertheless, he argued against the Doctor's morals and principles, saying that the war must continue and secure Gallifrey's victory at any cost and questioned him on why he refused to fight alongside his people, despite admitting that he didn't think the Doctor was a coward like a number of conscripts and Captain Tamasan had insisted he was. (AUDIO: The Conscript)