Final answer:
The president acts as the Commander in Chief of the Armed Forces, which gives them significant authority in military and foreign affairs as directed by the United States Constitution.
Step-by-step explanation:
When war breaks out, the president acts as the Commander in Chief of the Armed Forces. The president's military powers enable them to federalize the National Guard in times of war or national emergency. Within the realm of foreign and defense policy, the president holds significant authority. As Commander in Chief, the president decides the strategic military actions and has the power to wage war, which has increased in scope over time.
The United States Constitution, specifically in Article II, Section 2, explicitly states that the president shall be the Commander in Chief of the Army and Navy as well as the militia when called into service. This role is fundamental in guiding foreign policy and representing the United States in international affairs. Moreover, the president has the ability to appoint federal judges, ambassadors, and other officials to manage the nation's diplomacy and military strategy.