Semi-useless information: I believe the concept of burning the boats came from Tariq Bin Ziyad in his conquest of Spain, in the 8th century, whereby he actually burned his army's ships (whereas Cortes merely grounded his ships), and delivered this speech:
"Oh my warriors, whither would you flee? Behind you is the sea, before you, the enemy. You have left now only the hope of your courage and your constancy. Remember that in this country you are more unfortunate than the orphan seated at the table of the avaricious master. Your enemy is before you, protected by an innumerable army; he has men in abundance, but you, as your only aid, have your own swords, and, as your only chance for life, such chance as you can snatch from the hands of your enemy. If the absolute want to which you are reduced is prolonged ever so little, if you delay to seize immediate success, your good fortune will vanish, and your enemies, whom your very presence has filled with fear, will take courage. Put far from you the disgrace from which you flee in dreams, and attack this monarch who has left his strongly fortified city to meet you. Here is a splendid opportunity to defeat him, if you will consent to expose yourselves freely to death. Do not believe that I desire to incite you to face dangers which I shall refuse to share with you. In the attack I myself will be in the fore, where the chance of life is always least."