The United States dropped the first atomic bomb ever used in warfare on Aug. 6, 1945. Though the atomic bomb hastened Japan’s surrender and the end of World War II, it ushered in world annihilation fears and decades of arms races. The biggest threat to modern civilization is a nuclear weapon in the hands of irresponsible populists, former British diplomat Tim Willasey-Wilsey wrote in a recent essay. “The greatest danger of a massive global shock would come from the use of a nuclear weapon in anger for the first time since 1945,” he wrote. “A nuclear war will not be about an inability to join dots but another massive failure of human imagination.”