The most dramatic impact of Spanish military power, however, lay in the defeat of the American empires of the Aztecs and Incas. From 1519–21, a coalition army of Spanish soldiers and Tlaxcalan warriors led by Hernán Cortés and Xicotencatl the Younger defeated the Aztec Empire; in 1532, Francisco Pizarro and his brothers Gonzalo and Hernando invaded and occupied the Inca Empire from their base in Panama. Both wars in which very small numbers of Spanish soldiers – the conquistadors – who were mostly veterans of Spain's European or North African campaigns, were backed by local allies and defeated well established empires, shared many similarities. The highly proficient conquistadors benefited from their access to cavalry, steel swords, axes, spears, pikes, halberds, bows, crossbows, helmets and armour, not to mention small cannon, none of which were familiar to local forces. The Spanish also benefited from their immunity to many common European diseases which were to decimate their local enemies.