In his first essay in more than four months, Cuban leader Fidel Castro said that in the 1980s, North Korea provided Havana weapons "without charging a cent."

"Comrade Kim II Sung, a veteran and flawless fighter, sent us 100,000 Kalashnikov assault rifles and the corresponding (ammunition),” he wrote in a long, wide-ranging article taking up three pages of Communist Party newspaper, Granma.

"Only a few of us knew about this because it would have been very dangerous for the enemy to have that kind of information."

- Fidel Castro

Last month Panama detained a cargo ship carrying an undeclared shipment of arms including missile systems and live munitions that were bound from Cuba to North Korea. Havana has called it obsolete equipment and said it was being sent for repairs in North Korea.

In the article, Castro also touched on key Cold War moments such as the Cuban Missile Crisis and the failed Bay of Pigs invasion, and said Soviet Premier Yuri Andropov told him in the early 1980s that Moscow would not step in if Cuba were to be invaded by its northern neighbor.

"He said that if we were attacked by the United States, we should fight alone," Castro wrote. "We asked if they could supply us with free arms as (they had) up until that time. He said yes. We told him then: 'Don't worry, send us the weapons and we will take care of the invaders ourselves.'"

"Only a few of us knew about this because it would have been very dangerous for the enemy to have that kind of information," Castro said.

Castro, who turned 87 Tuesday with little fanfare, has made only a couple of public appearances this year.

In the essay, he said that when he became ill in 2006, he never thought he would have seven more years to live.

"As soon as I understood that it would be definitive I did not hesitate to cease my charges as president ... and I proposed that the person designated to exercise that task proceed immediately to take it up," the retired leader said, referring to his successor and younger brother Raul Castro, 82.

"I was far from imagining that my life would be prolonged seven more years," he added.

Castro also reflected on topics such as the death in March of his friend and close ally Venezuelan President Hugo Chavez, as well as the wonders of science.

"The sciences should teach us above all to be humble, given our congenital self-sufficiency," he said. "Thus would we be better prepared to confront and even enjoy the rare privilege of existence."

Castro stepped down as president following a near-fatal illness in 2006, and his successor, Raul, has said that his current term ending in 2018 will be his last, ostensibly ending nearly six decades of rule by the Castro brothers.

Based on reporting by The Associated Press.

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