Johnson is a lieutenant general of the United States Army.
He was Director of the Joint Improvised Explosive Device Defeat Organization from July 2013 till June 2015.Previously, Johnson was the commanding general of the Eighth United States Army and the Chief of Staff for United Nations Command, Combined Forces Command, and United States Forces Korea.
He has served in numerous command, staff, and teaching assignments throughout the world, including in Germany, Iraq, and South Korea.