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.
Regardless of federal law, the military services are allowed to impose more strict standards -- and many of them have. The maximum age for non-prior service enlistments for each of the services are: 1  Active duty Army - 35. 2  Army Reserves - 35. 3  Army National Guard - 35. 4  Active duty Air Force - 27.