Casement was a former British diplomat, who had since devoted himself to the cause of Irish independence. He was inspired by John MacBride's success in forming the Irish Transvaal Brigade, during the Boer War. Casement traveled to Germany by way of the United States, shortly after the outbreak of World War I, with the aid of the Irish Republican Brotherhood and the Clan na Gael. On December 27, 1914, Casement signed an agreement in Berlin, authorizing the brigade, with German Secretary of StateArthur Zimmermann. Only 56 Irishmen volunteered and they were brought together at a POW camp at Limburg an der Lahn.At its peak the brigade's Irish personnel consisted of: A military brigade usually has over 3,000 members, indicating its target size and the scale of Casement's optimism and failure. The intended Brigade was part of a much larger plan by Imperial Germany to involve Hindu nationalists and German-Americans, along with Irish nationalists, against their common enemy, Britain. Casement eventually became disillusioned with the German government. He came to believe that the Germans saw the brigade only as a potential diversion, assisting the Central Powers, and that they did not take Irish independence seriously. When he discovered that German material aid for the planned Easter Rising of 1916 was less substantial than expected, he abandoned the brigade and returned to Ireland by German submarine, in an effort to persuade the Irish Volunteers to cancel the rising. Shortly after his arrival on the coast of County Kerry, Casement was arrested, and later charged with treason against the United Kingdom and executed. A former sergeant in the Brigade, Daniel Bailey, was also arrested and turned King's Evidence against Casement, detailing his recruiting activities in Germany. By the time the 1916 rising took place, the Irish Brigade was defunct. A detailed account of Casement's Irish Brigade in Germany was written by Michael Keogh, recruiting officer and Sergeant Major in the Irish Brigade in Germany and Casement’s adjutant. The book was officially launched on 15 July 2010. A release of prisoners' statements by the UK National Archives in 2014 suggested that most of the 56 volunteers were persuaded by John Nicolson, an Irish-American priest, and not by Casement.