Easter Rising in putting the rising off for only a day, although it greatly reduced the number of Volunteers who turned out. British Naval Intelligence had been aware of the arms shipment, Casement's return, and the Easter date for the rising through radio messages between Germany and its embassy in the United States that were intercepted by the Royal Navy and deciphered in Room 40 of the Admiralty. The information was passed to the Under-Secretary for Ireland, Sir Matthew Nathan, on 17 April, but without revealing its source, and Nathan was doubtful about its accuracy. When news reached Dublin of the capture
Irish Citizen Army authorities tolerated the open drilling and bearing of arms by the ICA, thinking that to clamp down on the organisation would provoke further unrest. A small group of IRB conspirators within the Irish Volunteers movement had started planning a rising. Worried that Connolly would embark on premature military action with the ICA, they approached him and inducted him into the IRB's Supreme Council to co-ordinate their preparations for the armed rebellion which became known as the Easter Rising. On Monday, 24 April 1916, 220 members of the ICA (including 28 women) took part in the Easter Rising, alongside a much