For a visionary rabbi in London, the Balfour Declaration of 1917 signified nothing less than the advent of the messianic era.
http://mosaicmagazine.com/tesserae/2014/02/abraham-isaac-kook-receives-the-call/?mode=print
On November 2, 1917, Britain endorsed the creation of a Jewish national homeland in Palestine. The news, contained in the document thereafter known as the Balfour Declaration, hit Rabbi Abraham Isaac Kook like a thunderbolt.
A committed if decidedly unconventional Zionist, Rav Kook was then living in London, serving as the rabbi of an immigrant Orthodox community, continuing to elaborate the complex and dazzlingly original ideas that would fill volumes of philosophical, theological, and mystical writing, and building the reputation that would in time propel him to the position of founding chief rabbi of Jewish Palestine and one of the most enduringly influential shapers of modern Zionism and Jewish thought.
Born in Russia in 1865, Kook had begun life as a child prodigy, educated almost from infancy to scholarship and religious leadership. As a young man, in addition to mastering Talmud at the famed Lithuanian yeshiva of Volozhin and elsewhere, he studied secular philosophy and Hebrew with adherents of the Jewish “Enlightenment.” Broad as his interests were, however, and voracious as was his appetite for revolutionary ideas, Kook had taken almost no part in the early stirrings of Jewish nationalism. It was not until the early years of the 20th century that he emerged as a supporter of Zionism, and even then with reservations. In particular, he was skeptical of the secular brand of political Zionism promoted by Theodor Herzl, contending that a Zionism divorced from religion, and from a sacred reading of Jewish history, was destined for failure.