"We're frustrated," conceded President Obama's press secretary, Robert Gibbs, on Monday. The U.S. relationship with Afghan president Hamid Karzai is currently strained, to say the least. Offering some historical perspective on the situation, we welcome a guest post today from Michael H. Hunt, whose most recent book, A Vietnam War Reader: A Documentary History from American and Vietnamese Perspectives, was published in February. --ellen Sometimes history really does repeat itself. Consider this scenario: The U.S. government throws its support behind a leader in an important front in a global conflict. But after eight years of...