Sentence:  During the next five <WSD>years</WSD> liberal leaders in the United States sank in the cumulative confusion attendant upon and manifested in a negative policy of Containment - and the bitterest irony - enforced and enforceable only by threat of a weapon that we felt the greatest distaste for but could not abandon : 
Meaning of the word marked with <WSD> tags:  a period of time containing 365 (or 366) days