The President is both the head of state and head of government of the United States of America, and Commander-in-Chief of the armed forces. Under Article II of the Constitution, the President is responsible for the execution and enforcement of the laws created by Congress.
You can join some branches of the United States military at the age of 38 years but not others. The Army, Navy, Air Force, Marine Corps and Coast Guard each has its own minimum and maximum age requirements for enlistees, including for new recruits in the active-duty ranks, the Reserves and the National Guard.
There are five active branches of the Military. 1  Army â As the oldest branch of the Military, the Army protects the security of the United States and its resources. 2  Marine Corps â Working closely with the Navy, the Marine Corps is often first on the ground in combat situations.