 Complete the following phrase:  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 