Served in No.5 Commando July 1940 until December 1942.

07.06.1940 enlisted Belfast; civil trade Labourer; posted East Yorkshire Regiment.

08.06.1940 posted Infantry Training Centre, Beverley.

19.07.1940 volunteered for and joined No.5 Commando on formation, posted 10 Troop.

23.03.1942 No.5 Commando embarked for Madagascar (Operation Ironclad).

30.05.1942 appointed Lance Corporal, No.5 Commando.

09.06.1942 admitted to 11th General Hospital Antsirana, Madagascar, for 3 days.

20.06.1942 reverts to Private at own request.

29.06.1942 admitted to 11th General Hospital, Madagascar.

27.12.1942 posted No.2 Northern Command Infantry Depot after returning to the UK.

29.01.1943 permanently attached 11th Bn., Yorkshire Regiment (Green Howards).

14.03.1943 11th Green Howards, embarked for India (Draft RNAWZ).

23.06.1943 posted 2nd Bn., King's Own Scottish Borderers.

31.08.1943 admitted Hospital 4th Field Ambulance, injury to right arm and pneumonia.

31.08.1943 D1 List (RAMC); to x (II) List. Temporarily unfit.

13.09.1943 2nd Echelon, India, evacuated to No.9 Casualty Clearing Station.

In 1944 Private Brennan suffered 9 attacks of Malaria as well as Dysentry and Jaundice whilst in India and when deployed to the Arakan and Kohima, Burma, requiring hospital admission. 

---.01.1945 medically downgraded to C(I) and C(II) list with chronic malaria.
10.04.1945 medically evacuated Bombay for UK. Hospitalised UK on return.

31.10.1945 posted 10 Infantry Holding Bn.

07.11.1945 released on leave.

04.02.1946 Class 'A' Release.

"Military conduct very good. This man is of a most willing and cheerful nature. He will tackle most jobs with enthusiasm and can be relied upon to do a job to the utmost of his ability. Has served with the Commandos and specialised in demolitions. Can be recommended to future employers as a conscientious worker".