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.
Not All Branches Are the Same. When it comes to basic requirements, not all branches of the military are the same. The Air Force typically closes the door to recruits at age 27. The Marines close it at 29, and both the Army and Navy limit the maximum age to 34.