The President of the United States is the Commander-in-Chief of the Armed Forces.
All branches except the Coast Guard are part of the Department of Defense , which is controlled by the Secretary of Defense . The Coast Guard is part of the Department of Homeland Security . The Marine Corps is part of the Navy.
Usually, uniforms denote the bearer's rank by particular insignia affixed to the uniforms. Ranking systems have been known for most of military history to be advantageous for military operations, in particular with regards to logistics, command, and coordination; as time went on and military operations became larger and more complex, military ranks increased and ranking systems themselves became more complex.