Final answer:
Santiago digs in the dune by the pyramids to uncover treasure, reflecting the pursuit of destiny in 'The Alchemist'; analogous to strategic historical actions such as building fortresses for defense or conducting invasions.
Step-by-step explanation:
Santiago chooses to dig in the dune by the pyramids in order to uncover treasure. This question likely refers to the novel 'The Alchemist' by Paulo Coelho where the protagonist, Santiago, dreams of a treasure and his quest leads him to Egypt. The digging in the dunes symbolizes the pursuit of one's personal legend or destiny, an overarching theme in the book.
Similarly, historical and strategic considerations lead to constructions and actions such as the building of the Castillo de San Marcos, primarily to defend against imperial challengers, or the Bay of Pigs invasion which aimed to overthrow the government of Fidel Castro. These actions are driven by the desire to protect, gain strategic advantage, or seize perceived treasures of differing kinds.