The Armed Offenders Squad (AOS)is a specialist unit of the New Zealand Police designed to "cordon, contain and appeal to" armed and dangerous offenders. As the name explains, they are called upon when conflict with an armed offender has occurred or is considered imminent.
The AOS draw upon a varied arsenal of weapons and are often seen in heavy body armour. By contrast, most front-line police officers in New Zealand are lightly protected and do not normally carry firearms. The establishment of the AOS is an attempt to retain this situation (lightly armed police officers being the standard) and yet retain the ability to deal with offenders too dangerous for measures like pepper spray or a baton.
The Special Tactics Group (STG), formerly known as the Anti-Terrorist Squad, is the full-time tactical and counter-terrorism group of the New Zealand Police.
The STG is civilian police SWAT-type unit established to respond to high-risk situations which are beyond the scope or capacity of everyday policing. STG officers directly support operational police in incidents, such as sieges, with specialist tactical, negotiation, intelligence and command support services.