When he was 19 Garbold Azzaya left his grandparents and their cattle and sheep in the foothills of Bulgan in northern Mongolia and joined the army. Two years later, when he was a sergeant in the 150th Peacekeeping Battalion, he flew from a sub-zero Ulaanbaatar to the 40C (105F) heat of al-Hillah, near the ruins of Babylon, to man the guard towers of Camp Charlie, the headquarters of the multinational division in Iraq. Sixteen days after he arrived Sergeant Azzaya, armed with an AK47 six years older than he was, saw a blue car too close to the wall at...