What incident caused Castro and Cuba to be closely allied with Russia

it was the Bay of Pigs Fiasco. It was an invasion of Cuban exiles whose goal is to overthrow the government of Fidel Castro. It was launched in Guatemala by CIA-trained counter-revolutionary forces known as Brigade 2506. Though they were supported by American bombers who bombarded the Cuban airfields and managed to overwhelm a small militia, they were crushed by a Cuban counter-offensive by Jose Ramon Fernandez. Later, Castro himself led the attack and the invaders surrendered and were imprisoned on April 20, 1961.

it is the Bay of Pigs fiasco