For almost two years after the election of 1912, progressivism continued to define the political agenda of the United States. The outbreak of World War I in Europe during the summer of 1914 brought that situation to an end, and transformed the nature of partisan debate for the remainder of the decade. Once the United States had declared its neutrality in the conflict, questions of whether to intervene in Europe, the proper role for a neutral in the wake of the submarine weapon, and the shape of peace after the fighting stopped introduced new elements that accelerated some reforms and stifled others. The start of World War I thus marks a basic shift in American public life and the end of progressivism in its essentially domestic phase.