David Grann has a lengthy article in The New Yorker on William Alexander Morgan, a U.S. citizen who fought for Fidel Castro during the revolution, and then was executed by firing squad as he became an opponent of the new regime.
It was March 11, 1961, two years after Morgan had helped to overthrow the dictator Fulgencio Batista, bringing Castro to power. The revolution had since fractured, its leaders devouring their own, like Saturn, but the sight of Morgan before a firing squad was a shock. In 1957, when Castro was still widely seen as fighting for democracy, Morgan had travelled from Florida to Cuba and headed into the jungle, joining a guerrilla force. In the words of one observer, Morgan was “like Holden Caulfield with a machine gun.” He was the only American in the rebel army and the sole foreigner, other than Guevara, an Argentine, to rise to the army’s highest rank, comandante.
Interesting stuff, including J. Edgar Hoover, Rafael Trujillo, Robert F. Kennedy, and of course Che Guevara, who didn't like Morgan (they were the only two foreigners to hold the title of "Comandante").
Especially these days, when you see the geriatric dictatorship that Cuba has become, it can be hard to imagine how romantic the revolution was, and how much hope it generated at the beginning.