Dr. Owen Hunt first appeared at Seattle Grace in the Season 5 premiere, "Dream a Little Dream of Me." He immediately caught the eye of Dr. Cristina Yang as a tough-talking, bad-ass Army trauma surgeon.
A few episodes later, Dr. Hunt was added to the hospital staff full-time by the Chief as the Head of Trauma, which helped boost Seattle Grace's national rankings in that capacity. His outspoken, brash nature has caused some clashes with the other attendings so far, but Owen has also won the respect of the staff - and possibly the heart of Cristina.
Owen Hunt was a veteran of the Iraq War and held the rank of Major in the U.S. Army.