N1961, president john kennedy and his advisers tried to overthrow fidel castro by invading cuba with 1,400 cia-trained cuban exiles. nearly all the invaders were soon killed or captured, the united states was humiliated, and cuba allied itself more closely with the former ussr. this failure is attributed to

The Cuban Missile Crisis
You see Castro was annoyed that the US did this and he allied itself with the USSR.
At this time there was a arms race between the US and USSR.
So the USSR sent 80 MRBMs(medium range ballistic missies) to Cuba.
The bad thing was up untill this point both countries couldn’t hit each other beaicse rocket propulsion want that advanced and lacked range.
Now the Soviet msiisles could hit Washington.
So the US said they would take the action of missiles crossing the border as a threat of war.
We nearly got close to WW3 before Krucshchev the Soviet leader prevented the crossing.

The answer is b biology