The Haganah launched a campaign called the “Saison” or Season. They amassed information on the Irgun and Lehi, kidnapped Irgun fighters and gave the British lists of names of suspected members of the Irgun. During the Season, nearly one thousand people were handed over to the British and sent to Latrun detention camp or deported to Africa. Dozens of other suspects were kidnapped and detained in prison cells on various kibbutzim for interrogation and occassional torture. After public protests, the Season gradually dwindled.
In the summer of 1945, the British general elections swept the Labor government into power. They had pledged to revoke the White Paper and allow the survivors in the DP camps to immigrate to Palestine and work towards a homeland for the Jews in Palestine. However, Prime Minister Clement Atlee and Foreign Minister Ernest Bevin reneged on the pledge and re-confirmed the policy of the White Paper.
The Jewish leaders in Palestine were deeply disappointed. The Haganah changed its policy and entered upon a military struggle against British rule with the behind the scenes acquiescence of the Jewish Agency. They joined forces with the Irgun and Lehi to form the United Resistance Movement to drive the British from Palestine.
While Irgun and Lehi fighters were attacking military targets, the Haganah confined itself, initially, to assaults on targets connected with immigration. The culmination of Haganah activities was the destruction, in one night, of 11 bridges linking Palestine to the neighboring countries. “The Night of the Bridges” as the operation was known, was the largest the Haganah launched within the framework of the United Resistance, and was also its final one. The operation achieved its objective, and the country was cut off from all its neighbors.
In response, to the United Resistance Movement, the British planned a counter operation, Operation Agatha, which began on Saturday, June 29, 1946. It was known by the Jews as the Black Sabbath. A countrywide curfew was proclaimed, and 17,000 soldiers entered institutions and settlements in order to confiscate weapons and documents, and to arrest leaders of the Yishuv and Haganah activists. A considerable amount of intelligence information was collected, and thousands of Jews were arrested and jailed in special internment camps. Archives and a large number of documents including telegrams, which clearly proved the role of the Jewish Agency in the leadership of the united resistance, were seized from their offices and taken to the King David Hotel in Jerusalem.
Two weeks later, the Irgun responded by bombing the British headquarters at the King David Hotel, by planting exlplosives in the basement. The phone call warning of the attack and calling for evacuation was ignored and 91 people were killed in the explosion, 28 were British, 41 Arabs, 17 Jews and 5 others. The attack sent shockwaves around the world.
Although the attack had been approved by Moshe Sneh, the head of the Haganah, both the Haganah and the Jewish Agency distanced themselves from the attack and the United Resistance Movement disintegrated. The Irgun however, continued with their policy of attacking British military and government objectives.