That's not exactly correct. The Constitution also empowers Congress to grant letters of Marque and Reprisal.
Many pretend these don't exist, and that they're from a bygone era.
However, what they are are military or covert operations less than war that injure an enemy for reasons of reprisal or national security interest.
So, Congress can grant a letter to pursue an objective that injures an enemy, even militarily, but that is less than war.
His old man lectured on using letters of Marque and Reprisal. Ron, wanted to use them to go after OBL.
Secondly, Rand is wrong on War. A State is also empowered to engage in War. Congress and a State are the only principles that can do that.