R. Zvi Pesah Frank (1873–1960), chief rabbi of Jerusalem and halakhic authority, was born in Kovno, Lithuania. His father, R. Judah Leib, was one of the leaders of the "Haderah" society in Kovno which founded the village of Haderah in Erez Israel. He studied under R. Eliezer Gordon at Telz and under R. Isaac Rabinowitz at Slobodka. He attended the musar discourses of R. Israel Lipkin of Salant. In 1893 he proceeded to Jerusalem where he continued his studies at the yeshivot of Ez Hayyim and Torat Hayyim. He acquired an outstanding reputation, combining a profound knowledge of the Talmud with sound common sense. Despite his youth, he was encouraged by R. Samuel Salant, the rabbi of Jerusalem, who consulted with him in his halakhic decisions. In 1895 he married Gitah-Malkah, granddaughter of R. Hayyim Jacob Spira, head of the Jerusalem bet din. Subsequently he taught at a number of Jerusalem yeshivot. In 1902 he moved to Jaffa in order to be able to devote himself entirely to study. R. A. I. Kook had already taken up his appointment there, and later he and R. Frank associated in the efforts to establish the rabbinate of Israel.

In 1907 R. Frank was appointed by R. Salant and the scholars of Jerusalem as a member of the Bet Din Gadol in the Hurvah synagogue. Although he was its youngest member, the burden of the bet din, and the religious affairs of the city fell mainly upon his shoulders. He conducted single-handedly the spiritual administration of the city in the difficult days of World War I. The Turks tried to send him into exile in Egypt, but he hid in an attic from where he directed the rabbinical affairs of the city until the entry of the British (December 1917). The rabbinate was in a perilous state and Frank made strenuous efforts to raise its status, both materially and spiritually. He understood the importance of founding a central rabbinical organization, and immediately after the British occupation, took steps to found "The Council of Rabbis of Jerusalem." This organization, however, was short lived. Later, however, he established the "Rabbinate Office," which became the nucleus of the chief rabbinate of Israel, and on his suggestion R. A. I. Kook was invited to become chief rabbi of Palestine in 1921. In the violent controversy which resulted, fomented by the extreme religious section which saw no halakhic precedent for such an appointment, R. Frank brought proof to bear. In 1936 he was elected chief rabbi of Jerusalem. In consequence of his preeminence as a halakhist, the appointment was accepted by all parties, including those who opposed him on political grounds.

R. Abraham Isaac Kook (1865–1935), first Ashkenazi chief rabbi of modern Erez Israel. Rav Kook was born in Griva, Latvia in 1865. His father was a student of the Volozhin Yeshiva, the center of mitnagdut, whereas his maternal grandfather was a member of the Hasidic movement. He entered the Volozhin Yeshiva in 1884, where he became close to the Rosh HaYeshiva, Rav Naphtali Zvi Yehuda Berlin (the Netziv). Already in his youth, he was well known as a prodigy. At the age of 23, he entered his first rabbinical position. Between 1901 and 1904 he published three articles which anticipate the fully developed philosophy which he developed in the Land of Israel. In 1904, he came to the Land of Israel to assume the rabbinical post in Jaffa, which also included responsibility for the new secular Zionist agricultural settlements nearby. His influence on people in different walks of life was already noticeable, as he attempted to introduce Torah and Halakha into the life of the city and the settlements. The outbreak of the First World War caught him in Europe, and he was forced to remain in London and Switzerland for the remainder of the war. While there, he was involved in the activities which led to the Balfour Declaration. Upon returning, he was appointed the Rav of Jerusalem, and soon after, as first Chief Rabbi of Israel (though the state had not yet been been born). Rav Kook was a man of Halakha in the strictest sense, while at the same time possessing an unusual openness to new ideas. This drew many religious and nonreligious people to him, but also led to widespread misunderstanding of his ideas. He wrote prolifically on both Halakha and Jewish Thought, and his books and personality continued to influence many even after his death in Jerusalem in 1935. His authority and influence continue to this day. R. Kook was a prolific writer, who, according to his students, wrote out of the constant urge to create. He never attempted to construct a comprehensive system, and his style mirrors the quality of his personal insights and mystical reflections.