A

According to the US Constitution the President fulfills the role of the commander in chief of the military. As the Constitution states, the President is the supreme military commander.

Explanation:

In the year 1947, it was decided that the acting President of the US will perform the responsibilities of the supreme commander. The Constitution establishes that the President is the commander in chief “of all the armed forces of the United States comprised within the national military establishment – the Air Force, the Army, and the Navy.” Interesting to mention, that the grant of such power to the President has raised many disputes throughout American history. From one perspective, this position provides broad authority to the presidents and substantial powers. From another aspect, the Constitution does not give a clear definition of those powers, which lets some scholars claim that this is only to save the title of supremacy, rather than granting additional control.

It is also crucial to mention that the situation with the powers of the supreme commander in the US has changed after the dramatic events of September 2001. Due to the threat of terrorist attacks, the Authorization for Use of Military Force against Terrorists (AUMF) was passed in Congress. This legislation gave more expansive powers to the President, providing him with more significant opportunities to apply constitutional rights. Thus, due to the presidential course, it led to the invasion of Afghanistan as a response to the 9/11 attacks. According to the Supreme Court of the country, the presidential power as a commander in chief becomes more substantial when they gain the support of the Congress, as it happened with the case of AUMF.