Koestler was born poor in 1905, 120 years ago this month. A Hungarian Jew and a writer, he bounced around for a while, living for a short time in Palestine (the British Mandate) in 1926, and then working in Berlin for the infamous Russian Zionist Vladimir (later called Ze'ev) Jabotinsky.
I only know about Jabotinsky because I worked in the Pentagon 25 years ago, and all my bosses knew about him, and some idolized him. He is specifically known for "Revisionist Zionism," something I never heard of, because frankly, in the United States, there should be no need to be experts on the historical evolution of other people's founding ideologies.
Revisionist Zionism exchanges the ideas of Ben Gurion, of European and Russian Jews settling in the land of Palestine as individuals, for a more expansionist variation. Jabotinsky's Zionism came with the assumption of Jewish sovereignty over the entire region, not only the River to the Sea, but covering both sides of the Jordan River, and far beyond.
Bibi has the map, and we think about it, if we think about Israel at all, as Greater Israel. It's pretty big for 9 million Jews to manage, but like Sparta, there are millions of helots to help. We'll come back to this technicality in a second.