Why did Soviet ships turn back on their way to Cuba? US ships had formed a naval quarantine around Cuba.
The Soviet Union had sworn not to interfere in Cuba.
Fidel Castro had proclaimed that the ships could not dock in Cuba.
The United Nations had issued a medical quarantine of Cuba.

us ship had formed a naval qurantine around cuba

Explanation:

tenochtitlan (also spelled tenochtitlán), located on an island near the western shore of lake texcoco in central mexico, was the capital city and religious centre of the aztec civilization. the traditional founding date of the city was 1345 ce and it remained the most important aztec centre until its destruction at the hands of the conquering spanish led by hernán cortés in 1521 ce, which led to the final collapse of the aztec empire.