Illegal immigration to Palestine can be traced back to the era of the Ottoman Empire. In the initial phase of the British Mandate, there was little need for such immigration, as British policy allowed a significant number of Jews to settle in Palestine. However, with the rise of Hitler and the subsequent surge in Jewish emigration, Revisionist groups began organizing small cohorts of illegal immigrants.

In 1938, the Histadrut established the Mossad L'Aliyah Bet as a central coordinating body for illegal immigration. Prior to the outbreak of World War II, 41 ships carrying around 16,000 illegal immigrants reached Palestine. Throughout the war, efforts to facilitate illegal immigration persisted. Between 1939 and 1944, 26 vessels set sail, mainly from Bulgaria and Romania, with five sinking en route. In total, 16,500 individuals embarked on the journey to Palestine during the war, while an additional 3,740 immigrants entered the region via land routes.

In the aftermath of World War II, over 600,000 displaced Jews remained in Europe. From 1945 to 1948, 69,000 of these individuals were transported from Europe by ship. Although most of them were intercepted by British vessels and subsequently interned in Cyprus, illegal immigration highlighted the urgent need for a Jewish state to accommodate Jewish refugees.

A significant number of these illegal immigrants ultimately found themselves in British detention camps located in Cyprus.