Unfortunately, the Constitution does not define "enemies" or "waging war".
Well it specifies that Congress must declare war.
However, be that as it may. If you are interested you could examine the Burr treason trial wherein Chief Justice Marshall gave the definitive definition of “treason” under which our nation has operated for the 200 years since.
The trial is very instructive of the true nature of Thomas Jefferson and gives a portrait of him unknown to people today. And it is not pretty.