Douglas Clark Denham

Searching for Army history

That was very minimal information to work with, but I suppose that it concerns the following person:
https://nashonomroll.org/f_nominalroll2.asp?NominalRollID=106536

You could try here:
https://www.defence.gov.au/about/accessing-information/personal-information-requests

FYI - It mentions:
The personal information of an ADF member can be requested by:
Current member
Ex-member
Immediate family of a current or ex member, living or deceased
Advocate or representative of a living current or ex member
Advocate or representative of the immediate family of a deceased ex-member.

There are Battalion and Unit Diaries you can research online at the Australian War Memorial, or if you’re locating specific service records you can try these links:

National Archives of Australia: Session expired | RecordSearch | National Archives of Australia

Virtual War Memorial (this may show photographs): https://vwma.org.au/

I hope this helps.

Ruth