Mattis joined the Marines in 1972 and commanded at every level over four decades — the 1st Marine Division into Iraq in 2003, I Marine Expeditionary Force, Joint Forces Command, NATO's Supreme Allied Commander Transformation, and finally US Central Command until 2013. He became the 26th Secretary of Defense in 2017 and left in 2019 over the withdrawal of American forces from Syria. In 2015, out of uniform and speaking to a private audience, he s…