The Second Aliyah (1904–14) began after the Kishinev pogrom; some 40,000 Jews settled in Palestine, although nearly half of them left eventually. Both the first and second waves of migrants were mainly Orthodox Jews, although the Second Aliyah included socialist groups who established the "kibbutz" movement. Though the immigrants of the Second Aliyah largely sought to create communal agricultural settlements, the period also saw the establishment of Tel Aviv in 1909 as the "first Hebrew city." This period also saw the appearance of Jewish armed self-defense organizations as a means of defense for Jewish settlements. The first such organization was Bar-Giora, a small secret guard founded in 1907. Two years later, larger Hashomer organization was founded as its replacement. During World War I, British Foreign Secretary Arthur Balfour sent the Balfour Declaration to Baron Rothschild (Walter Rothschild, 2nd Baron Rothschild), a leader of the British Jewish community, that stated that Britain intended for the creation of a Jewish "national home" in Palestine.