Kings Will Be Tyrants by Ward Hawkins is a 1959 novel about fighting in Cuba. Bernardo Manuel Patrick O'Brien is a former U.S. Marine who winds up fighting for Castro. Though a Marine, he has to deal with the conflict of his heritage, both Cuban and American.
According to Ed Sullivan of The Sunday Ledger-Enquirer: "Hawkins does a pretty good job of writing an action story, compelling on the surface, but sadly lacking the spice of underlying causes and effects which make such stories not only readable but valuable footnotes to history."