 Sometimes, time plays an important role in strategic situations. Things take step one after the other, and not only do they do, but the actors know that they will and that influences how they behave. So the year was 1519, and Nan Cortez, Spaniard, was leading a flotilla of 11 boats, and about 600 men about to invade a continent later to be known as America. They were vastly outnumbered and were well aware of the heavy odds they were facing. And as is famously known, as they landed, Cortez ordered that all the boats be burnt. There's some controversy whether this was done in complete coordination and agreement with his men, or it was sprung on them. But either way, it's clear what the logic behind it was. The Cortez knew that as they faced these daunting odds, the men would be tempted to turn back, board the boats, and flee. And by removing that option, that increased their fighting resolve going forward. And so, again, there's not only the fact that time passes between actions, but that one reasons about that fact and impacts how the strategic situation unfolds. We see it not only when there are multiple agents involved, but even in a single decision maker here, it's not only Cortez and his men, the two actors, or the two sets of actors who somehow actions are intertwined, but even when there's a single actor, the fact that time unfolds can impact the situation. Here's another famous historical tale in this case of Ulysses and the Sirens. Ulysses is captaining his boats and about to pass through the Straits of the Sirens. And as is commonly known, the Sirens' song are so seductive that they would cause any person in particular Ulysses to do things that are not in his own best interest. He would jump into the sea, he would crash the boat against the rocks. And so what he does, according to the tale, he orders all his men to first put their wax in the ears so they will not be seduced by the song. He himself, who in fact wants to hear the song knowing that he would not be able to withstand the seduction, orders his men to tie him to the mast and should he possibly get free from the ties to restrain him with his swords. And so it comes to pass. They sail through the Straits. When he hears the Sirens' song, he goes temporarily insane and tries to escape from the bonds and fails. And all is good. So here again is a single actor in this case, Ulysses, reasoning about the future, thinking about what will the situation be and taking action now to impact what the strategic situation will look like in the future. To model such a situation, we turn to games in extensive form, as the term is called, sometimes simply known as game trees.