from Victor Davis Hanson in National Review Online, The Costs of Abandoning Messy Wars

Donald Trump has rightly reminded us during his campaign that Americans are sick and tired of costly overseas interventions. But what Trump forgets is that too often the world does not always enjoy a clear choice between good and bad, wise and stupid. Often the dilemma is the terrible choice between ignoring mass murderer, as in Rwanda or Syria; bombing and leaving utter chaos, as in Libya; and removing monsters, then enduring the long ordeal of trying to leave something better, as in Afghanistan and Iraq.The choices are all awful.

But the idea that America can bomb a rogue regime, leave, and expect something better is pure fantasy.

Because we spend more time demonizing the leaders than trying to understand the circumstances of their decisions, we fail to learn the lessons.  Thus those who criticized the Bush decisions in Iraq and only spoke of his incompetence, proceeded to make the same mistake in Libya only a few years later.