The New Zealand Army will hold a military exercise from today until Wednesday at the harbour, Hampden, Mt Stalker Station and Herbert Forest.
The exercise is called Antium.
About 40 soldiers from the 2/1 Royal New Zealand Infantry Regiment at Burnham Military Camp will take part.
A New Zealand Defence Force spokesman said the event involved soldiers operating in built-up areas.
"They will be practising, and then will be tested, on night operations in an urban area.
"The soldiers will be operating mainly by night, in a covert fashion, to gather information on a role-playing enemy provided by other soldiers from 2/1 RNZIR."
One of the appealing aspects of Oamaru Harbour area was that it was secure and allowed the army to create the best possible scenario.
The public could expect to see the army using its Pinzgauer all-terrain vehicles.