Sentence:  Cuban S. S. R. : Whatever may have been the setbacks resulting from the <WSD>unsuccessful</WSD> attempt of the Cuban rebels to establish a beachhead on the Castro held mainland last week , there was at least one positive benefit , and that was the clear-cut revelation to the whole world of the complete conversion of Cuba into a Russian dominated military base . 
Meaning of the word marked with <WSD> tags:  failing to accomplish an intended result