To accommodate the growing population and those who would be forced from the center by the construction of new boulevards and squares, Napoleon III issued a decree in 1860 to annex eleven communes (municipalities) on the outskirts of Paris and increase the number of arrondissements (city boroughs) from twelve to twenty. Paris was thus enlarged to its modern boundaries with the exception of the two major city parks (Bois de Boulogne and Bois de Vincennes) that only became part of the French capital in 1920.