The SAS is one of New Zealand's most celebrated and mythical fighting forces. Though frequently shrouded in secrecy, it has been the target of intense scrutiny in recent years.
After an SAS member died following a training accident in Auckland on Wednesday night, the spotlight is again on the elite force.
Defence analyst Paul G Buchanan from 36th Parallel Assessments said SAS training was necessarily tough, and would remain so, but he expected the SAS to investigate the death seriously.
The trooper was taken by helicopter to Auckland City Hospital, where he was later pronounced dead, the New Zealand Defence Force said in a statement.
The NZDF said it would hold a Court of Inquiry, and police were investigating what happened on behalf of the coroner.
"The soldier's family has been informed and are being supported at this sad time," the NZDF said in a statement on Thursday morning.
PREMIER COMBAT UNIT
The Special Air Service was formed in 1955 and is the Defence Force's premier combat unit.
SAS troopers have been deployed throughout the Pacific region, south-east Asia, and in Afghanistan.
Their presence in Iraq has been the subject of frenzied speculation but recent governments have generally avoided discussion about SAS operations in that country.
Buchanan understood the SAS had been involved in tracking Isis leaders in the quest to find captured Kiwi nurse Louisa Akavi.
The SAS is capable of counter-terrorism and overseas special operations and disposing of biological weapons and explosives.
Papakura Military Camp in south Auckland is the SAS base. Two years ago the SAS was welcomed into a new $46 million purpose-built building with reinforced rubber blocks capable of withstanding 10,000 rounds of ammunition.
"The most rigorous part of the SAS, other than being behind enemy lines and trying to fight for your survival, is the selection course," Buchanan said.
He said SAS training could include night-time parachute jumps, live fire exercises and close-quarter combat.
Training could be nuanced, tailored to the terrains and climates of places the SAS could be deployed to.
Buchanan said an example might be training to fight an Isis-type force in a Middle Eastern city.
"You have to be able to distinguish between friend and foe in the dark. All that needs tremendous practice."
Previously, only military personnel could apply to join the SAS.
But entry had recently been opened to civilian applicants. Selection usually takes place twice a year.
Buchanan said perhaps 80 per cent of people "wash out" during training and did not make it to the next level.
In 2016 an SAS trooper told Stuff that passing selection was just the start of a three year process towards becoming a fully SAS member.
The Defence Careers website said others who might not be selected could pursue their other "trade" option and continue a career with the Army.
The SAS motto "Who dares wins" is also that of several other elite forces worldwide, including the British SAS.
SAS IN ACTION
There are four main roles within the SAS, according to Defence Careers.
The first is surveillance and reconnaissance, involving operating in complex terrain and difficult situations, often for long stretches on multiple missions and tasks.
Next is combating terrorism, and potentially responding to terrorist situations to support police, if the Government asks.
"They completely missed the Christchurch shooter and that's a failure of intelligence that never came to them," Buchanan said.
"It takes a while to muster these guys out of Papakura or wherever they may be."
The third role is described as "direct action", or conducting conducting complex, joint special operations, for short strikes to recover designated personnel – such as any mission to rescue "secret hostage" Akavi.
The final official role, "support and Influence", involved organising, training and advising host nation military and para-military forces to maintain internal security.
Defence Careers said that also involved helping other New Zealand government agencies conduct "national strategic operations".
Willie Apiata was awarded the Victoria Cross in 2007 for bravery under fire in Afghanistan.
He later established an organisation to help soldiers reintegrate into civilian life and has repeatedly been named at the top of New Zealand Reader's Digest Trust Surveys.
Doug Grant became the first member of the SAS to die in combat since the Vietnam War when he was shot in Afghanistan in 2011.
His widow, Sergeant Tina Grant, has since taken on the role of family liaison officer with the Defence Force, supporting families after a loved one dies in action.
French photographer Philip Poupin photographed Apiata in Afghanistan in 2010 and the publication of his image sparked debate among newspaper editors and politicians.
Allegations about three SAS raids in 2010 in Afghanistan's Tirgiran Valley influenced the publication of Jon Stephenson and Nicky Hager's book Hit and Run.
The book unleashed a political firestorm and as Stuff reported last year, the Defence Force assembled a special unit to defend the SAS against claims its soldiers were responsible for Afghan civilian deaths.
The Government's Operation Burnham inquiry is inspecting claims from Hit and Run, which alleged Afghani civilians were killed and 15 injured in the SAS operation.