In a series of revolts starting in 1820, four military officers rode forth on horseback from obscure European towns to bring political freedom and a constitution to Spain, Naples, and Russia; and national independence to the Greeks. The men who launched these exploits from Andalusia to the snowy fields of Ukraine--Colonel Rafael del Riego, General Guglielmo Pepe, General Alexandros Ypsilanti, and Colonel Sergei Muraviev-Apostol--all hoped to overturn...