Who is Adelai Stevenson from Thirteen Days; a Memoir of the Cuban Missile Crisis and what is their importance?

The U.S. Ambassador to the United Nations, Stevenson suggests in the National Security Council meeting withdrawing missiles from Turkey and Italy and giving up the Guantánamo Bay base as a good faith gesture. JFK has long felt the obsolete Jupiter missiles should go, but Guantánamo Bay cannot be abandoned under threat. RFK disagrees with Stevenson's recommendation but feels it is courageous, sensical, and adds to the discussion. As a former presidential candidate and leading liberal spokesman, Stevenson carries more weight in Ex Comm than his official position warrants.