http://historymatters.gmu.edu/d/5154#:~:text=In%20an%20atmosphere%20of%20World,and%20resident%20aliens%20from%20Japan. This is the Link to FDR Executive Order 9066
The conclusion is that although a US president can technically send troops into a foreign country, in order to lawfully declare war, he or she must get the approval of Congress.
