"The terms of the disagreement over a strong executive go back to the classic debate between Hamilton (as Pacificus) and Madison (as Helvidius) in 1793-94. Hamilton argued that the executive power, representing the whole country with the energy necessary to defend it, cannot be limited or exhausted. Madison replied that the executive power does not represent the whole country but is determined by its place in the structure of government, which is executing the laws. If carrying on war goes beyond executing the laws, that is all the more reason why the war power should be construed narrowly. Today Republicans and Democrats repeat these arguments when the former declare that we are at war with terrorists and the latter respond that the danger is essentially a matter of law enforcement.
As to the contention that a strong executive prompts a policy of imperialism, I would admit the possibility, and I promise to think carefully and prayerfully about returning Texas to Mexico. In its best moments, America wants to be a model for the world, but no more. In its less good moments, America becomes disgusted with the rest of the world for its failure to imitate our example and follow our advice. I believe that America is more likely to err with isolationism than with imperialism, and that if America is an empire, it is the first empire that always wants an exit strategy. I believe too that the difficulties of the war in Iraq arise from having wished to leave too much to the Iraqis, thus from a sense of inhibition rather than imperial ambition," - Harvey C. Mansfield, in the WSJ.
I belive that the difficulties of the war in Iraq arise from the fact that the Bush administration never actually decided between inhibition and imperialism, and chose a fatal path between two courses. But one lesson Machiavelli surely taught: if you are going to invade and occupy, invade and occupy. If you are going to leave, leave.