Like Lincoln Potus did not wait to declare war on the Socialists, the Confederates, the Demz, he just did it because of his Oath to the Constitution.
Immediately after inauguration?
Immediately after taking the Oath?
You'll SEE.
Lincoln found the power he needed to deal with the rebellion in the commander-in-chief clause of the Constitution, in the clause of Section II requiring him to “take care that the laws be faithfully executed,” and in his presidential oath “to preserve, protect, and defend the Constitution of the U.S.”
https://ashbrook.org/publications/onprin-feb2009-owens/