 The first one was during the Northern Campaign (March–November 1937), followed by a second wave after the fall of Catalonia (January–February 1939), in which about 400,000 people fled to France.The French authorities had to improvise concentration camps, with such hard conditions that almost half of the exiled Spaniards returned.The third wave occurred after the War, at the end of March 1939, when thousands of Republicans tried to board ships to exile, although few succeeded.