If you ask when, the answer is that you cannot make a single stroke between day and night. The precise moment does not matter. There was no painted sign to say, "You now are entering Imperium." Yet it was a very old road and the voice of history was saying: "Whether you know it or not, the act of crossing may be irreversible." And now, not far ahead, is a sign that reads: "No U Turns."

— Garet Garrett

It is difficult to pinpoint the moment at which America crossed from Republic into Empire but guidelines exist for doing so. In his treatise Rise of Empire (1952), the libertarian journalist Garet Garrett declared the "first requisite of Empire" to be "the executive power of government shall be dominant." Arguably, the power most intimately connected to Empire or imperialism is conducting foreign policy, especially war.