Aliyah Bet
During 1933–1948, the British government limited Jewish immigration to Palestine with quotas, and following the rise of Nazism to power in Germany, illegal immigration to Palestine commenced. The illegal immigration was known as Aliyah Bet ("secondary immigration"), or "Ha'apalah", and was organized by the Mossad Le'aliyah Bet, as well as by the Irgun. Immigration was done mainly by sea, and to a lesser extent overland through Iraq and Syria. Beginning in 1939 Jewish immigration was further restricted, limiting it to 75,000 individuals for a period of five years after which immigration was to end completely. During World War II and the years that followed until independence, "Aliyah Bet" became the main form of Jewish immigration to Palestine. Despite British efforts to curb the illegal immigration, during the 14 years of its operation, 110,000 Jews immigrated to Palestine.