Therefore, in a world filling up with saber-rattling and bad vibes, perhaps our best guarantee of peace is that major powers aren’t familiar with recent examples of successful wars. While Genghis Khan or Julius Caesar would invade a foreign country at the drop of a hat, present-day nationalist leaders such as Recep Tayyip Erdogan of Turkey, India’s Narendra Modi, and Israel’s Benjamin Netanyahu talk loudly but are very careful about actually launching wars.