The Jewish Legion idea was turned down by the British Commander. “Under the law, I am not entitled to accept foreigners into the British army. I can offer you only one thing: to form a mule transport unit from your young people and send it to a different Turkish front.” Jabotinsky felt that this was an insult to the Jews, and refused. Trumpeldor saw little difference between trenches and transport, and agreed. The officer appointed by the British to command the Jewish muleteers was John Henry Patterson. His second-in-command was Trumpeldor. In April 1915, the Assyrian Jewish Refugee Mule Corps (soon known as the Zion Mule Corps), sailed from Egypt to Gallipoli with several hundred men and 750 mules. They quickly distinguished themselves transporting water, ammunition, food, and other supplies to the front lines.

The Zion Mule Corps was deactivated in May 1916, but the British soon needed more manpower. In July 1917, Patterson was promoted to full Colonel, and began organizing the Jewish Legion. Acknowledging that he had been wrong about the Zion Mule Corps, Jabotinsky now accepted a commission as recruiting officer for the Jewish regiment. Among the thousands of Legionnaires were 120 former muleteers, a large contingent of Russian Jews from London, and a mixture of foreign nationals from Allied and neutral nations. Eventually, 150 American Jewish volunteers joined the Jewish Legion, as well as a further 1,000 Palestinian Jews. Prominent Legionnaires included Israel’s first prime minister, David Ben Gurion, and the father of another future premier, Yitzhak Rabin.

On February 2nd, 1918, the day before embarking for Egypt, the Jewish Legion marched through London’s Jewish quarter. The Jewish Chronicle reported: “...thousands of Jews and Jewesses marched merrily together with the ‘Judeans’ from the Tower whence the march began after they had been addressed by Colonel Patterson, who rode at the head of the picturesque Jewish troops.”

In June, the Legion was transferred to Palestine under the command of the Egyptian Expeditionary Force (EEF) commanded by General Sir Edmund Allenby, who was notoriously antagonistic towards Zionist aspirations. He was also opposed to the Balfour Declaration of November 1917, which promised the Jews a homeland in Palestine.

After successfully participating in the liberation of Damascus just before the end of the war, the Judean Regiment was pared down from three battalions to one. The remaining Legionnaires faced open discrimination from the British military authorities. Britain announced it was establishing a permanent army of occupation in Palestine, but turned down a large contingent of American Legionnaires who volunteered to serve in this force.

By 1921, all that remained of the Jewish Legion was a mixed Arab-Jewish militia headed by former Legionnaire Eliezer Margolin. When anti-Jewish riots in Jaffa left 13 Jews dead, Margolin led armed Jewish militiamen into the city to protect the Jews. For this breach of discipline, he was forced to resign. This effectively marked the end of the Jewish Legion.

In 1932, a group of American, Canadian and Argentinian former Legionnaires founded a moshav (agricultural settlement) called Avichayil (Father of the Army) near Netanya. Here they built Beit Hagdudim (Legions House), a museum dedicated to Patterson and the Jewish battalions of World War I. Colonel John Henry Patterson died in 1947, just a year before the establishment of the Zionist state that he had always supported.