Felipe IV's oath of allegiance to the Constitutions in Lleida in 1644 led to an increase in the numbers of those who supported a return to the Hispanic monarchy. The outbreak of plague in 1650 decimated the population. In October 1652, after a siege lasting 12 months, Barcelona surrendered, though the struggle continued in the north of the Principality. On 7 November 1659, the French and Hispanic monarchs signed the Treaty of the Pyrenees, a declaration of peace that ceded the counties of Roussillon and La Cerdanya to France, which was never accepted by the Catalan authorities. The institutions in the counties were abolished and in 1700 the use of the Catalan language in public was banned.