David Hartsough knows how to get in the way. He has used his body to block Navy ships headed for Vietnam and trains loaded with munitions on their way to El Salvador and Nicaragua. He has crossed borders to meet “the enemy” in East Berlin, Castro’s Cuba, and present-day Iran. He has marched with mothers confronting a violent regime in Guatemala and stood with refugees threatened by death squads in the Philippines.Waging Peace is a testament to the difference one person can...