It is generally agreed that neo-Orthodoxy in Germany began with the publication of Nineteen Letters on Judaism (1836) by Samson Raphael Hirsch (1808-1888), his first book, and declined upon the disintegration of the community and its institutions on the eve of World War II. The main hypothesis of this essay is that, contrary to this claim, further development of neo-Orthodox thought can be seen in the State of Israel as well, as expressed by its adherents over some fifty years. It should be emphasized that we are not dealing here with a self-declared stream of neo-Orthodoxy in Eretz Israel; rather, analysis of the theological and Zionist thought of neo-Orthodox followers, together with similarities in their biographical and social background, raise the possibility of regarding them as a unique stream within religious Zionism during the Yishuv period and the early years following the establishment of the State of Israel. The Zionist motivation of those adherents of modern neo-Orthodoxy, who, for the most part, immigrated to Eretz Israel in the 1930s and 1940s, stemmed primarily from a desire to transform Judaism in its Halakhic sense into the foremost component of the identity, culture, and lifestyle of Jewish society in Eretz Israel. This ideology, rooted in the philosophy of Halakha held by neo-Orthodoxy and by the historical-positivist stream, underlies the thought and activism of the figures discussed in this study, and set them apart from other religious streams during the Yishuv and early statehood period. However, the cultural atmosphere in Eretz Israel in the period from the early 1940s, when the concept of political independence acquired a practical dimension, to the late 1970s, when Israeli intellectual and social discourse began to change, put them at the forefront of the struggle over the national and cultural identity of Israeli society, against two opposing streams. The first of these was hard-line Orthodoxy and its rejection of any change in Halakhic ruling necessitated by the desire to make Halakhic Judaism the theological basis of modern Jewish society, while mystical and messianic trends which had taken over the center of religious Zionism were growing stronger. The second opposing stream was socialist Zionism, which constituted the Zionist leadership during the formative Yishuv and early statehood period. Socialist Zionism, inspired by the secular Jewish Enlightenment, basically sought to design a ‘new Jewish society’ founded upon the values of the tie to the land; the Hebrew language; and the Bible, in its socialist reading. It is clear that the different portrayal of Jewish society envisioned by followers of neo-Orthodoxy, on the one hand, and by socialist Zionism, on the other, set the two streams on an inevitable collision course. When the figures discussed here immigrated to Eretz Israel during the 1930s, it marked a new phase in the development of neo-Orthodox thought, to a great extent; its adherents were now required to put the validity of their vision of ‘all-inclusive Halakha’ to the test. This attempt, discussed in the third section, is symbolized by their participation in the settlement enterprise of the religious kibbutz movement. As we know, the religious settlement movement did not comprise only German immigrants to Eretz Israel; these were joined by groups of Hasidim from Eastern Europe. However, it would seem that the uniqueness of the figures discussed here is reflected in the Halakhic motivation for their endeavors to establish religious settlements. Contrary to the Eastern European groups, who regarded physical labor and communing with nature as a means for achieving individual transcendence, the adherents of neo-Orthodoxy regarded religious settlement activity as an important experiment for determining whether Halakha could serve as the means for forming a modern Jewish community in Eretz Israel, as an initial phase toward applying this vision to society at large. However, since rabbinical authorities ignored the Halakhic modifications needed by religious farmers, and the movement lacked political influence, the religious kibbutz movement, after years of struggle, reconciled itself to maintaining only the communal structure. This process reflected the gradual decline of neo-Orthodoxy in Israel.