Starting in 1939, a clandestine immigration effort called Aliya Bet was spearheaded by an organisation called Mossad LeAliyah Bet. Tens of thousands of European Jews escaped the Nazis in boats and small ships headed for Palestine. The Royal Navy intercepted many of the vessels; others were unseaworthy and were wrecked; a Haganah bomb sunk the , killing 267 people; two other ships were sunk by Soviet submarines: the motor schooner was torpedoed and sunk in the Black Sea by a Soviet submarine in February 1942 with the loss of nearly 800 lives. The last refugee boats to try to reach Palestine during the war were the "Bulbul", and "Morina" in August 1944. A Soviet submarine sank the motor schooner "Mefküre" by torpedo and shellfire and machine-gunned survivors in the water, killing between 300 and 400 refugees. Illegal immigration resumed after World War II.