Coal was critically short in the unusually cold winter of 1916-17. The outer neighborhoods of the city, particularly the 13th, 14th, 15th and 18th arrondissements, became centers of the defense industry, producing trucks, cannons, ambulances, and munitions. A large Renault factory at Boulogne-Billancourt made tanks, while a new factory in Javel mass-produced artillery shells; when the war ended, it became the first Citroën factory.