R. Israel Ze’ev Horowitz (1880–1918), Palestinographer. Horowitz was born in Tiberias, the son of R. Phinehas Horowitz, and was educated at yeshivot in Jerusalem. In the late 1900s he began a large work, Mehkerei Erez Avoteinu ("Studies of the Land of our Fathers"), of which he published only the first part, about the borders (1910). During World War I Horowitz taught Talmud at a modern religious school to support his family and at the same time began compiling an encyclopedia on the historical geography of Erez Israel, Syria, and Sinai called Erez Yisrael u-Shekhenoteha ("Erez Israel and her Neighbors"). He continued this work during the war, collecting material for 4,000 entries, while his family subsisted on the halukkah distributed by the Hungarian community. The entries from alef to yud were published posthumously by his son Abraham (d. 1957) in 1923; the article on Jerusalem (edited by his son) as a separate volume in 1964; the others were never published. The importance of Horowitz' work lies in the comprehensiveness of the talmudic sources which he quoted or cited in extensive footnotes. The text however suffers from Horowitz' inadequate scientific training and lack of scientific literature. He nevertheless ranks as one of the foremost authorities on the talmudic sources of the topography of Erez Israel.

R. Abraham Isaac Kook (Kuk, 1865–1935) was a rabbinical authority and thinker; first Ashkenazi chief rabbi of modern Erez Israel. Born in Greiva (now Griva), Latvia, R. Kook received the type of Jewish education that was customary in 19th-century Eastern Europe. At a very early age he showed independence of mind and far-reaching curiosity. Desirous to supplement his traditional education which was restricted to the study of Talmud, he undertook the study of the Bible, Hebrew language, Jewish and general philosophy, and mysticism. In 1888 he was appointed rabbi of Zaumel, and in 1895 became rabbi of Bausk (now Bauska). In 1904 he immigrated to Erez Israel, where he served as rabbi of Jaffa and the surrounding towns. There he fostered close ties with people of all shades of opinion and belief. He identified with the Zionist movement, thus antagonizing the rabbinical establishment, and at the same time, engaged in a vigorous debate with the irreligious pioneers and laid the foundations for a Religious Zionism that did not settle for the political pragmatism of the Mizrachi (the Religious Zionist Movement) or that of Binyamin Ze'ev Theodor Herzl, the founder of the Zionist Movement, but sought to view Zionism as a process of redemption, of repentance, and of an overall Jewish renaissance. Rabbi R. Kook was a man of complexity whose persona unified opposing spiritual worlds: the Lithuanian Torah scholarship with the hasidic spiritual experience, a commitment to halakhah and Jewish tradition with a modern worldview and Western culture and philosophy, a tendency towards spirituality and mysticism with full involvement in the practical matters of rabbinic and public leadership. In his effort to urge traditional Jews to fulfill the Zionist ideal, he traveled to Europe in 1914 to participate in a conference of Agudat Israel. Unable to return to Erez Israel because of the outbreak of World War I, R. Kook spent the war years 1914–18 in Switzerland and accepted a temporary position as the rabbi of the Mahzikei ha-Dat congregation in London, where he was very active in trying to influence the Jews of England to back Zionist political activity. Upon returning to Palestine after the war, R. Kook was appointed chief rabbi of Jerusalem, and with the formation of the chief rabbinate in 1921 he was elected the first Ashkenazi chief rabbi of Palestine.

R. Kook developed his own views on the role of Zionism in Jewish history. He held that the return to Erez Israel marked the beginning of divine redemption (athalta di-ge'ullah), and that the Balfour Declaration of 1917 had ushered in a new era in the renewal of the Jewish people. However, in his view, the existing Zionist movement was incomplete insofar as it had taken up only the revival of the secular and material needs of the Jewish people. In the beginning of 1918 he published an open letter, in which he called upon Jews the world over to help in setting up the Degel Yerushalayim movement, which was to emphasize the spiritual aspects of the national revival. For a short while R. Kook's movement created some interest. However, this interest soon spent itself, and before long, the movement was entirely forgotten.