 In June 1947 , Castro learned of a planned international expedition to invade the Dominican Republic and overthrow its right @-@ wing president , Rafael Trujillo , a military general and U.S. ally . Widely seen as a dictator , Trujillo utilized a violent secret police which routinely murdered and tortured opponents . Becoming president of the University Committee for Democracy in the Dominican Republic , Castro decided to join the expedition , led by Dominican exile General Juan Rodríguez . Launched from Cuba , the invasion began on July 29 , 1947 ; it consisted of around 1 @,@ 200 men , most of whom were exiled Dominicans or Cubans . However , the Dominican and U.S. governments were prepared , and soon quashed the rebellion . Grau ’ s government arrested many of those involved before they set sail , but Castro escaped arrest by jumping off of his naval frigate and swimming to shore at night . 
