 In the periods comprising the 1 to 22 April 1916 and 30 April 1916 to 31 March 1917, Peter, again serving under William P. Hanahan up until his arrest and from then on Donnchadh Hannigan, carried out military orders and instructions from commanding officers.As a consequence of this, he was arrested by British forces at Ballylanders in July 1916 and detained in the Military Detention Barracks Cork for two weeks.Before and after his arrest, Peter took part in the making of ammunition, preparing for military service, drilling, and carrying despatches.