In just about three months, 196 active-duty and retired officers are scheduled to go on trial in Turkey, charged with plotting in 2003 to overthrow the then-newly elected Justice and Development Party (AKP) government. The alleged coup plot—codenamed Operation Sledgehammer—involved horrifying acts, including the bombing of mosques and the downing of a Turkish fighter, aimed at destabilizing the government and paving the way for martial law and eventual takeover. If the charges prove to be well-founded, the country’s powerful military establishment will stand disgraced for harboring violent, anti-democratic elements among its senior ranks. And it will be the first time...