Conversation so far:
How did the Australian Mining Corp start?
David used his advocacy and organisational abilities to set up the Australian Mining Corps.
What year did this happen?
August 1915.
Was this a military endeavor?
David wrote a proposal to Senator George Pearce, the Australian Defence Minister, suggesting that the government raise a military force to undertake mining and tunnelling.
Do you know how old he was when this happened?
25 October 1915 he was appointed as a major, at the age of 57.
So he was in control of it.
Did he win any honors or mentions for this?
In January 1918, David was awarded the Distinguished Service Order and in November he was promoted to lieutenant colonel.
When did he leave this position?
The war having concluded, he was demobilised in 1919.

Question: What was his unit in charge of?
Self-contained rewrite: What was David's unit in charge of?