A military disaster is the defeat of one side in a battle or war which results in the complete failure of the losing side to achieve their objectives. It often, but not always, involves a high and disproportionate loss of life. The causes are varied and include human error, inferior technology, logistical problems, underestimating the enemy, being outnumbered, and bad luck. Entries on this list are those where multiple sources dealing with the subject of military disasters have deemed the event in question to be a military disaster (or an equivalent term). Ancient era Battle of Marathon (490 BC). A large Persian force was destroyed and routed by a smaller Athenian force. Battle of Salamis (480 BC). A huge Persian fleet was defeated by a united Greek force. Syracuse Expedition (415–413 BC). A large force from Athens failed to conquer the city of Syracuse, weakening the Athenian military position and depriving the city of much-needed manpower. Battle of Gaugamela (331 BC). Alexander the Great annihilated a much larger Persian army, thus ultimately conquering the Middle-east. Battle of Cannae (216 BC). Hannibal destroyed the 16 Roman and Allied legions led by Lucius Aemilius Paullus and Gaius Terentius Varro. In all, perhaps more than 80 percent of the entire Roman army was dead or captured (including Paullus himself). Battle of Zama (202 BC). A Roman army of 34,000 under Scipio Africanus annihilated the Carthaginian army of 50,000 under Hannibal, thus bringing an end to the Second Punic War. Battle of Carrhae (53 BC). Crassus with 40,000 soldiers marched into Parthia, expecting to be victorious, chose to march a direct route through the desert instead of the mountains of the north. He and his army were entirely annihilated by 9,000 Parthian soldiers. Battle of Teutoburg Forest (9 AD). Germanic warriors destroyed three Roman legions. Battle of Adrianople (378 AD). The Emperor Valens was killed while Gothic heavy cavalry ambushed and decimated his Roman heavy infantry. Medieval era Battle of Tours (732). The Muslim Moors marched into southern France meeting no foes, until encountering the Christian Frankish forces led by Charles Martel at Tours. Despite the Moorish advantage over the Franks militarily, they were defeated decisively by the Franks. Battle of Hattin (1187). Overconfident Crusader forces from Jerusalem became trapped in a waterless desert area, and thus became easy prey for the Muslim forces of Salah-ud-din (Saladin) Battle of Agincourt (1415). A large French