Conversation so far:
When did Prince Harry leave the Army?
Prince Harry left the army in June 2015.
When was Prince Harry seconded to the Australian Defence Force?
Prince Harry spent four weeks throughout April and May 2015 at army barracks in Darwin, Perth and Sydney whilst seconded to the Australian Defence Force (ADF)

Question: What did he do while on duty?
Self-contained rewrite: What did Prince Harry do while on duty?