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.
Service Branches Compared. Full Time i Full-time members of the Military live on base or in military housing and are immersed in military culture. Part Time i Part-time service members train one weekend a month and two weeks a year, which means they can pursue a civilian career or college. As the oldest branch of the U.S. Military, the Army protects the security of the United States and its resources.