FitzGerald joined the Irish Volunteers in 1914 and organised a Volunteers group in County Kerry. As an organizer he was expected to drill even the most unsuited recruits. This offended his disciplined morality. The organization was under enormous pressure: many leaders were expelled in July 1915 under the Defence of the Realm Act 1914. FitzGerald took the place of Ernest Blythe. In 1915 FitzGerald was imprisoned for making a speech against recruitment during the First World War. He was later expelled from Kerry, and moved to County Wicklow. FitzGerald's abstemious, parsimonious character, backed up by a long Anglo-Norman family history, made him an unpopular figure in the movement. He felt his bosses were unaware of his situation. During the occupation of the General Post Office during the 1916 Rising, he commented "I was bemused by the general attitude of security". At the height of the battle he was in the midst of the conflagration that shook the GPO garrison. Ever the sceptic, FitzGerald, who was in charge of rations, mentions in his memoir of the 1916 Rising the sudden and unexpected mobilisation, followed by a description of conditions in the GPO, the rebels' headquarters. While many accounts describe the Rising as a form of blood sacrifice, FitzGerald discussed its wider rationale with the leader Patrick Pearse, and with Joseph Plunkett who had travelled to Germany in 1915 for assistance. They expected that Germany would win the First World War, and that a rising of at least three days would allow Ireland to take a seat at the peace conference. Though declaring an Irish Republic in 1916, they considered it would probably be necessary to invite the Kaiser's youngest son Joachim to reign over a reformed kingdom of Ireland after the war, where Irish was to again become the everyday language.