How did Francisco Pizarro and 168 Conquistadors Defeat the Incan Empire?

How could the massive Inca Empire have been conquered by Francisco Pizarro and just 168 Spanish conquistadors? Pizarro and his men were the first Europeans to make contact with the vast Inca Empire, high in the Andes Mountains. In less than a decade, the Spaniards defeated the entire Incan army, hundreds of thousands of warriors strong.