Jimmy Carter was not a president of the first rank, but he managed by dint of unceasing effort to become an iconic world leader, with an inspiring, if often contentious, legacy as a dogged peacemaker and a decent and ethical problem-solver. His presidency—beset by a horrible economy, the Soviet invasion of Afghanistan and the seizure of American hostages in Iran —was a stunning political failure but a greater substantive success than was recognized when he was crushed for reelection by Ronald Reagan in 1980. In today’s world of perpetual military intervention, it’s striking that not a single bomb was dropped or shot fired in combat by American forces on Carter’s watch, and his leadership helped prevent at least five wars—in Panama, Israel, and Iran when he was president, and in Haiti and North Korea after he left office. The Camp David Accords he engineered proved to be the most successful treaty since the end of World War II. Long before he died Sunday, Dec.…