The 34th Indian Brigade was formed in Mesopotamia in December 1915 with four battalions newly arrived from India. It joined the 12th Indian Division to replace the 33rd Indian Brigade that was broken up on 7 December. While with the division, it took part in the Affair of Butaniya on 14 January 1916. The division never reached full strength as units were constantly detached to support the efforts to relieve the 6th (Poona) Division besieged at Kut. The division was broken up on 10 March 1916 and the brigade joined Corps Troops before it was posted to the new 15th Indian Division in May 1916.