The implied powers of the executive branch include the power to make use of the military without Congressional permission. Scholarly interpretation of the Commander-in-Chief clause of the Constitution differs on whether or not the implied powers exist.
There are some scholars whose interpretation of the Commander-in-Chief clause of the Constitution give the President no limits on his implied powers over the military. There have been instances in U.S. history where the Supreme Court has agreed with the President calling on his implied powers. During WWII, President Roosevelt used these implied powers to place all Japanese-Americans in internment camps. This decision was upheld by the Supreme Court in the decision on the case of Korematsu v. United States.
The Supreme Court has repeatedly handed down the decision that the President's powers regarding the military are limited because broader powers are not explicitly granted by the Constitution. In 1973, Congress passed the War Powers Resolution bill requiring the President to communicate with Congress about troop deployment and to remove troops if Congress disapproves. Despite these legal measures, U.S. Presidents have continued to make use of these implied powers without consequence. The Korean War, the Vietnam War, Operation Desert Storm, the Afghanistan War of 2001 and the Iraq War of 2002 took place because of presidents invoking their implied powers without Congressional consent.