The letter from Fidel Castro that surfaced on the front page of the state newspaper Granma on Tuesday served two purposes. The first was proof of life. When you’re the founder of a state and your physical condition is subject to almost constant rumor, you don’t arrange to be photographed holding up a copy of a current newspaper to prove that you remain alive. You remark on events that have recently transpired, and make that front page your own.

Which was of course the other thing the senior Castro, 88, accomplished: Leaving his mark—however belatedly, guardedly and obtusely—on events that have largely been out of his hands since he handed over power to his brother Raul in 2006, owing to failing health. Tuesday’s remarks were Fidel’s first since since the momentous simultaneous declaration on Dec. 19 by Raul and President Barack Obama that Cuba and the U.S. would begin to…