Overconfidence and War

I got my grubby little hands on a copy of Dominic D.P. Johnson's Overconfidence and War: The Havoc and Glory of Positive Illusions. The book looks great and I can't wait to read it. President Flightsuit, quite appropriately in my opinion, adornes the front cover. You can almost see the hubris dripping from his smirk. Based on what I've read so far, it sounds like it couldn't be more relevant to the situation we face in Iraq and the general trends of our foreign policy over the last four years. I'm only about four pages in, but I wanted to share this brief anecdote that opens the book:
On 16 November 1532 the Spanish explorer Francisco Pizarro and his modest force of 168 men attacked and defeated an Inca army of 80,000 soldiers at Cajamarca in Peru. Despte the incredible asymmetry in manpower, the Spaniards apparently won by means of superior weaponry and the effects of their opponents' surprise at the novelty of cannon, horses, and trumpets. The greater mystery is what led the conquistadors to believe they could win. There are accounts of the whole valley being full of Inca soldiers, filing out of their huge encampment for most of the morning. What gave the Spaniards the audacity to stay and fight?
Just in case you deduce from this that overconfidence is a good thing, Pizarro's story is immediately contrasted to Custer. I'll try to pass along interesting tidbits as they come up.