GROZNY, Dresden, Guernica: some cities have made history by being destroyed. Aleppo, once Syria’s largest metropolis, will soon join their ranks. Its 1,000-year-old Muslim heritage has turned to dust; Russian aircraft have targeted its hospitals and schools; its citizens have been shelled, bombed, starved and gassed (see article). Nobody knows how many of the tens of thousands who remain in the last Sunni Arab enclave will die crammed inside the ruins where they are sheltering. But even if they receive the safe passage they have been promised, their four-year ordeal in Aleppo has blown apart the principle that innocent people should be spared the worst ravages of war. Instead, a nasty, brutish reality has taken hold—and it threatens a more dangerous and unstable world.