Final answer:
Cuba felt the need to strengthen its defenses after the Bay of Pigs due to the difficulty for the U.S. to overthrow the Castro administration, the Soviet Union's military protection, and increased hostility towards the United States.
Step-by-step explanation:
After the Bay of Pigs invasion, Cuba felt the need to strengthen its defenses due to several reasons.
Firstly, the failed invasion highlighted the difficulty for the United States to overthrow the Castro administration, which made Cuba realize the importance of being prepared against future military plots.
Secondly, the Soviet Union stepped in and provided military protection to Cuba, causing Cuba to strengthen its defenses in order to deter any future invasions.
Lastly, the failed invasion and subsequent events, such as the Cuban Missile Crisis, increased Cuba's hostility towards the United States, leading to the belief that a strong defense was necessary to protect its sovereignty.