Illegal Jewish immigration to Palestine during the British Mandate was one of the most spectacular enterprises organized by the Jews in the first half of the 20th century before the creation of the state of Israel. The Jews called such immigration ‘Type B’ (Aliyah Bet), to differentiate it from the official type (aliyah) allowed for by British authorities. Aliyah Bet was an indication of the diaspora's longing to return to the Promised Land, and simultaneously a way of fighting the restrictive policy of Great Britain which limited Jewish immigration to Palestine. It was also a form of aid to Jewish refugees from Europe and salvation for Jews menaced by Nazism. In due time Aliyah Bet became a national myth, part of the Jews' collective consciousness.

This book deals with Aliyah Bet activity in the years 1934–1944. It opens with the organization of the first sea transport of illegal immigrants to set sail for Palestine (the ship Velos, in July 1934). That date is considered the symbolic beginning of Aliyah Bet, though the phenomenon was known to exist from much earlier. The closing bookend of the book's chronology is December 1944 and the last wartime sea transport (the ship Taurus). Thus two entirely different chapters in the history of Aliyah Bet form the subject of my analysis: the period when the movement was forming and becoming organized, and the war years – a time of great challenges and even greater difficulties. The book does not address the postwar period (1945– 1948), a subject to which a decidedly varied literature has already been devoted; this decision was dictated by the need to focus on issues which had received relatively little attention in previous research.