Which character is a former Army trauma surgeon?

The Grey’s Anatomy character who was a former Army trauma surgeon is Owen Hunt.

Owen is introduced in season 5 as a U.S. Army surgeon who served in Iraq and held the rank of major. His military background shapes his direct, unconventional approach to emergency medicine and surgery. His first dramatic appearance involves treating a wounded man with an improvised tracheotomy.

After returning from Iraq, Owen joins Seattle Grace Hospital as the head of trauma surgery. His combat experiences also contribute to post-traumatic stress disorder, which affects his relationships and decision-making. He is sometimes confused with Teddy Altman, a fellow military doctor and former Army colleague, but Owen is the character specifically established as the Army trauma surgeon.