Final answer:
The Soviet government explained their reason for placing nuclear missiles in Cuba as a response to perceived aggression from the United States. President Kennedy implemented a naval quarantine to prevent further missile shipments to Cuba.
Step-by-step explanation:
The Soviet government explained that placing nuclear missiles in Cuba was a response to perceived aggression from the United States. President Kennedy's speech aimed to justify the U.S. blockade of Cuba and convey a strong stance against the Soviet Union. He decided to implement a naval quarantine (blockade) around Cuba to prevent further missile shipments. In this context, quarantine refers to the blockade or restriction imposed by the United States on Soviet shipments to Cuba.