Fire officers only come to the aid of police officers once or twice a year, and only in rural communities, the Fire Service says.
Fire officers were called to help Constable Perry Griffin when he was knocked to the ground at Kawhia wharf on Friday evening by a group who allegedly kicked him, and took his Taser, radio and pepper spray.
Volunteer fire fighters were asked to help following a call from the Police Northern Communications Centre.
The Fire Service said it is very rare for police to ask for a volunteer fire brigade to help a police officer.
National operations manager Stu Rooney said, in these cases, firefighters were not police officers and have no power to arrest people.
"They respond as any member of the local community would, and do their best to calm down the situation and provide a neutral presence. Four people in yellow bunker coats turning up with an appliance can give those involved in an altercation something else to think about."
Kawhia chief fire officer Callan Stewart said he and the six other members of his brigade who responded to the local police officer's call for assistance on Friday evening did their best to calm people down.
"We have a lot of members who are women, and they are 'aunties' to many local people.
"What we tried to do when we arrived was first get all the holidaymakers and children who were in the area to leave," he said.
Three people appeared in Hamilton District Court on Saturday on charges stemming from the attack.
The attack was the fifth on a Waikato officer since just before Christmas.
Police Commissioner Peter Marshall said it was a concern that the officer's Glock pistol could have been taken from him.
But he told Radio New Zealand the officer had made "the right decision" not to draw the weapon.
"When I was speaking to the senior volunteer fire officer at Kawhia, he said if the firearm had been withdrawn, anything could have happened in that pack mentality."
Mr Marshall said there were 62 one-person stations throughout the country, including on the Chatham and Pitcairn islands, but single-officer stations were not the subject of "any undue assaults".
"It is a rare occasion. It shouldn't be happening. It does happen, unfortunately. Policing is inherently dangerous."
Police Association vice president Stuart Mills said Mr Griffin would have been safer if a second officer was present, and police should reconsider how sole-charge officers tackled dangerous situations.
"There have been far too many of these serious assaults on police officers. Policing is dangerous, however this type of injury on a regular basis, as has been seen recently, should not be occurring," he told Radio New Zealand.
The Labour Party has promised to double the number of officers at sole-charge stations, and reiterated the call in light of the recent attacks.
In a statement to Radio New Zealand, Police Minister Anne Tolley said Labour was using the attack to score cheap political points.
She said police deployed staff as they saw fit.