Clashes in the capital between Habré's FAN and pro-Libyan groups became progressively more serious. On 22 March 1980, a minor incident, as in 1979, triggered the Second Battle of N'Djamena. In ten days, the clashes between the FAN and Goukouni's FAP, which both had 1,000–1,500 troops in the city, caused thousands of casualties and the flight of about half the capital's population. The few remaining French troops, who left on 4 May, proclaimed themselves neutral, as did the Zairean peace force.