Administrative correspondence relating to the prisoner of war relief scheme set up at Birr Castle under the patronage of Lady Rosse; postcards and letters of thanks from the prisoners of war from Irish regiments (but predominantly the Irish Guards) interned in Germany; and acknowledgment postcards of parcels received from same.

Photograph album created by Lt. Col. M. O'Carroll Fitz-Simon, M.C. , who began his military career in Prince of Wales' Leinster Regiment, which was headquartered at Birr. The photographs document a peace-keeping mission the Leinsters undertook in Silesia (now part of Poland) from their departure at Dover on 31 May 1921, through Germany and to their destination of Oppeln (Opole in Poland today). Following the disbandment of the regiment in June 1922, Fitz-Simon joined the King's Own Regiment, Lancaster and the remaining photographs in the album depict scenes from missions in India and Burma. There is also a small number of photographs of people and houses in the Birr area including Whigsborough House, and the burnt out remains of Birr Barracks (following its destruction in the Civil War in July 1922).

Preprinted acknowledgment postcards sent by return by prisoners-of-war in German camps on receipt of relief parcels organised by the Birr Castle scheme. Personal details recorded include name, rank and internment camp.