20 May Washington Post - Iraq Isn't Like Vietnam -- Except When It Is by Robert Dallek.

These days, it's not terribly original to say that the Iraq war is like the Vietnam War. Many doves use the comparison lazily, invoking Vietnam to urge the United States to pull out. Like most historical analogies, it's a pretty inexact one. (For one thing, Vietnam began as a guerrilla war and ended as a conventional one, while Iraq began as a conventional fight and degenerated into an insurgency.) But having studied President Lyndon B. Johnson's descent into the Vietnam abyss, and having just spent several years poring over Vietnam-era papers and tapes from President Richard M. Nixon and Henry Kissinger, I've found that some of the parallels sound disturbingly familiar today. They're not perfect, but they're instructive -- and give us a disquieting sense of how hard it can be for policymakers to learn from history...