Why would Cuba feel the need to strengthen its defenses after the Bay of Pigs?

The Cuban government was afraid the United States might invade again

After the Bay of Pigs, Cuba would understandably try to strengthen its defenses. The reasons for this are that the country was directly attacked on its own soil. The United States obviously wanted to take down their government and even invade the country. Most of the people that left the country because of the government were obviously ready to fight against Cuba if sponsored and backed by someone. In order to secure its territory and integrity, Cuba had to invest heavily in its army so that the country's defenses can be on higher level in case something similar happens again.