The production of armaments became the highest economic priority in the belligerent countries, and the need for factory workers in such industries exploded. Enemy occupation of France's great industrial bastion meant that new centers of heavy industry had to be created in Paris and in the central and southern provinces. By the close of 1915, the population of Paris stood at nearly double its prewar size. A belt of cities stretching from Rouen in the north to Marseilles and Grenoble in the south now provided much of France's industrial strength. In the southern city of Toulouse the prewar gunpowder factory employed 100 workers; by November 1918, it required 30,000. In Britain the population of London swelled steadily, and the new munitions centers set up by Lloyd George in 1915 continued to draw in workers. But the flow of migrants moved in other directions as well: the call for agricultural workers drew Englishwomen out of the cities and onto the land. In Germany, industrial centers like Essen and Dortmund and shipyard cities like Danzig and Kiel grew. Meanwhile, the call-up of men reduced the population of Berlin and Hamburg. France became, next to the United States, the most important destination in the world for foreign migrants. A flood of laborers, half a million strong, poured in, the majority coming from Spain, China, and the Asian and African portions of France's empire. In the small industrial town of Le Creusot, the working population in the spring of 1918 included 1,700 Chinese, 240 Algerians, and over 400 workers from the Iberian peninsula. Without counting prisoners of war, also an outside presence in the community, the total foreign work force reached 2,770.