During the 1936–1939 Arab revolt hundreds of Jews were killed by Arabs but the Yishuv leadership didn't respond. The militant group known as the Irgun embarked on an intensive armed campaign against Arab targets. Later British targets were added also. With the outbreak of World War II, militant actions against the British were halted, but one of the leaders of the group, Avraham Stern, insisted that the fight must go on, leading to a split in the Irgun which led to the formation of a new group, Lehi (also known as the Stern Gang or Stern Group). In 1944, the Irgun, now headed by Menachem Begin rejoined the fight against the British. After the end of World War II, the larger Haganah joined the fight within a union called the Jewish Resistance Movement, which lasted for just about ten months, from October 1945 until August 1946.