On his arrival, he and Ben Zvi went on a tour of 35 cities in an attempt to raise a Hechalutz "pioneer army" of 10,000 men to fight on Turkey's side.[2] They succeeded in recruiting 63 volunteers.[3] After the Balfour Declaration of November 1917, the situation changed dramatically and Ben-Gurion, with the interest of Zionism in mind, switched sides and joined the newly formed Jewish Legion of the British Army, leaving to fight the Turks in Palestine.