The Vietnam War was our longest—longer than the Civil War and the two world wars. It rent our society as no other issue had done since the War Between the States, and the wounds it inflicted have yet to completely heal. With its conjoined ordeal, Watergate, it raised distrust of government to new levels. It affects our attitudes toward war to this day; we are still struggling to define our nation's interests abroad.
A less recognized but significant aspect of the Vietnam War is that it was our transitional war: our first war of counterinsurgency, against an enemy in the midst of the very people we were trying to defend and that melted back into the population after striking. A war against both a state (North Vietnam) and an ideological revolution (communism), it frequently involved unorthodox combat. Up against a far weaker opponent—in conventional terms—we learned the limits of traditional military power; our B-52s did not subdue a tough and determined enemy. Since Vietnam, the concept of power has radically changed.