So whatever Constitution you're talking about is not ours.
Article I, Section 8 of the U.S. Constitution indicates that Congress has the power to declare war. On the other hand, Article II, Section 2 of the Constitution identifies the President as the “Commander-in-Chief” of all U.S. military forces. Traditionally, this has been interpreted to mean that only the Congress can declare war, and that once that is done, the President will be responsible for leading those military activities.
This distinction has also been interpreted to mean that the President can take steps to act defensively of the national interests, but cannot take preemptive military action. In other words, under the U.S. Constitution, the President is only authorized to repel invasions and sudden
attacks without a formal Congressional declaration of war. Any undeclared offensive military actions are not executive branch powers.