The Cuban Missile Crisis had just ended, with Soviet leader Nikita Khrushchev’s promise to President John F. Kennedy on Oct. 28 1962 that he was withdrawing his strategic nuclear weapons from the island.

But nearly 100 smaller Soviet nuclear warheads were also in Cuba, unknown to the U.S. government at the time and for decades into the future.

Fidel Castro wanted desperately to keep them.

Had Castro prevailed, Cuba would have become a nuclear power. And if Kennedy had known that Khrushchev had all but lied on Oct. 28, the hawks in Washington might have won their push for an all-out U.S. invasion of the island.

Instead, Soviet Deputy Prime Minister Anastas Mikoyan, sensing that the “hothead” Castro could not be trusted with any nuclear weapons, got them out of Cuba after telling him that Soviet law did not permit the transfer of nuclear weapons to other countries.

“It is a pity. And when are you going to repeal that law?” Castro asked Mikoyan during a tense meeting on Nov. 22, 1962, according to a new book by his son, Sergo Mikoyan, and researcher Svetlana Savranskaya.

It’s been 50 years since the Cuban Missile Crisis, Oct. 16-28, when the world came closer than ever to a U.S.–Soviet nuclear war and nightmarish terms like Armageddon and “mutually assured destruction” — MAD — became almost real.

Research in recent years has shown the crisis impacted a broader swath of the world than previously known, said James Hershberg, editor of the book series published by the Cold War International History Project at the Woodrow Wilson Center in Washington.

Moscow’s concessions to Kennedy likely pushed North Korea to launch its own search for nuclear weapons, one study showed. Another argued that it led North Vietnam to step up its armed campaign against the south.

But Sergo Mikoyan’s book, The Soviet-Cuba Missile Crisis, focuses on the crisis in Havana in November of 1962, as his father jawboned with Castro to clean up the loose ends of the Cuban Missile Crisis

“The headline here is just how close Cuba came to being a nuclear power,” said Hershberg, whose book series includes the Mikoyan work.

The book includes 50 Soviet government and Mikoyan family documents, including official notes from the Mikoyan-Castro talks. Sergo Mikoyan died in 2010 and Savranskaya, a researcher at George Washington University’s National Security Archive, completed the book.

The tale essentially starts after Khrushchev tells Kennedy Oct. 28 that he will withdraw from Cuba the “weapons which you call offensive” — Soviet R-14 and R-12 missiles with nuclear warheads and ranges of up to 1,550 miles, and medium-range IL-28 bombers, aged but still capable of carrying nuclear bombs.

What Khrushchev did not reveal was that 98 tactical nuclear warheads also had been deployed in Cuba for the Luna and FKR-1 missiles, both coastal defense weapons deployed essentially to destroy a possible U.S. invasion armada.

In the weeks leading up to the Missile Crisis there had been conversations between U.S. and Soviet officials about the Soviet Union sending Cuba weapons so that it could defend itself, according to documents released Thursday from the archives of Robert F. Kennedy, then the attorney general and an advisor to his brother.

But with the United States apparently unaware such weapons had nuclear capabilities, the tense exchanges between the two Cold War powers centered on the removal of weapons “capable of offensive war,’’ not the weapons that could be used to repel a possible U.S. invasion.