"It's not that New Zealand has been pushed into this.
"This is the price of an independent foreign policy,'' Prof Patman, of the University of Otago politics department, said yesterday.
"New Zealand is probably facing its most challenging international security context since the end of the Cold War,'' he added.
"New Zealand's core goal is maintaining a rules-based international system, and it wants to have an independent foreign policy.''
New Zealand had to "walk the talk'' and could not just say "we're giving up our military capability'' and lecture other countries on our preferred outcomes.
New Zealand could not rely on superpowers such as the United States or China to advance our national interests, and needed sufficient resources to maintain our independent stance.
The Government has announced it aimed to buy the Super Hercules aircraft to replace its current, ageing C130 Hercules aircraft, some of which have been flying for more than 50 years.
This is part of a wider $20billion investment plan for the New Zealand Defence Force between now and 2030, and also includes replacing other ageing aircraft with four Boeing P-8A Poseidon maritime patrol aircraft from the US Government.
If New Zealand had been "naive'' before the Christchurch terrorist attack which had killed 51 people, we could no longer imagine that our distance from many other countries would automatically protect us from further terrorism risks, Prof Patman said in an interview.
New Zealand had one of the largest economic exclusion zones in the world, covering 11% of Earth's surface and needed modern aircraft to patrol that zone, as well as to bring help to Pacific nations threatened by climate change-related weather emergencies, and undertake evacuations, if required, he said.