This article examines two runs of Percy MacKaye's community masque Caliban by the Yellow Sands, a huge outdoor show involving over 1500 chiefly amateur participants and seen by tens of thousands of spectators. The masque was first performed at New York Lewisohn Stadium from 24 May through 5 June 1916, as part of the American celebrations of the three-hundredth anniversary of Shakespeare's death. Its second production was mounted at Boston Harvard Stadium from 2 through 21 July 1917. Both renderings had roughly the same plot and structure, but the circumstances of their performance differed dramatically: during the New York run, America was still maintaining its neutrality in the First World War, whereas the Boston show occurred shortly after the USA joined the conflict on 6 April 1917. This article uses the two productions of Caliban as the starting point for an exploration of the uses of Shakespeare in the contemporaneous debates concerning America's involvement in the First World War. It traces the ways in which the powerful cultural icon of Shakespeare was appropriated to support the changing political agendas of the period which witnessed the USA's move from neutrality to entering the war on the side of the Allies.