The operation stretched from a busy Pretoria shopping centre to a small police station north of the city yesterday.
One of the three people arrested was the commissioner of the Rust de Winter police station, Captain Petrus Badenhorst.
Investigators of the Hawks' crimes against the state unit, explosives experts and specialised forensics investigators, sealed off sections of the Rust de Winter police station - after raiding Badenhorst's house - confiscating safes and registers and questioning officers at the station.
It was expected that other properties in Bela Bela, north of Pretoria, would be raided last night, and more people would be arrested.
The syndicate, which is believed to have operated for the past year, is suspected of stealing police and military ammunition and weapons from the station's armoury and allegedly selling it to criminals involved in cash-in-transit robberies and other crimes.
The sting, outside the McDonald's restaurant at the Kolonade shopping centre, played out after police officers posed as arms buyers after infiltrating the gang and befriending the "middlemen", a Pretoria couple. They convinced them to show them ammunition available for sale.
A police informant had tipped off the Hawks about the syndicate.
Investigators were hand-picked to run the top-secret case.
Early this month undercover operatives carried out the first phase of the operation, buying more than 10000 rounds of semi-automatic and handgun ammunition.
Days later, another sale was arranged and detectives bought tens of thousand of rounds of ammunition.
The two sales led to yesterday's sting operation.
Waiting for the ammunition delivery, officers - who were to buy the ammunition for R28000 - carefully laid their trap, positioning vehicles to block any escape routes.
Arresting the couple, who are both in their late-30s, police seized hundreds of boxes of police-issued 9mm and shotgun rounds as well as nearly 1000 military-issue R1 bullets hidden beneath a baby blanket in the couple's blue Uno.
Hours later the officers were led to Rust de Winter police station and later raided Badenhorst's home, seizing ammunition and a safe believed to have contained hundreds of thousands of rands in cash.
With Badenhorst's wife hurling abuse at officers, police arrested the commander when he arrived home from a provincial police briefing in Bela Bela.
A detective involved in the raid, who cannot be named, said the scale of theft was "monumental".
"It is clear that this is well organised. It is organised crime, [allegedly] being committed by one of our own. Here we are trying to stop crime and our very own are [allegedly] helping to commit it.
"They were helping criminals to wage a deadly war."
The policeman said Badenhorst allegedly ensured he was in a position to run a carefully planned arms-smuggling "business".
"He made sure he was the only one who had access to the armoury, keeping all the keys to himself," said the officer.
"He was also the only one with access to the firearm and ammunition registries, which we are seizing," he said.
With the festive season fast approaching, the race is now on to recover the stolen weapons and ammunition from heist gangs before they strike.
Hawks spokesman Captain Paul Ramaloko said the case was one of the most serious involving alleged police corruption.
"The implications of what this officer has allegedly done are immense. We are following up information that the weapons and ammunition have been sold to organised crime syndicates," he said.
Ramaloko said the Hawks had been watching the three suspects - who will appear in the Pretoria North Magistrate's Court tomorrow - for months.
The ammunition recovered was estimated to be worth nearly R1-million.
"Information indicates the suspects were allegedly dealing in and smuggling stolen ammunition for some time.
"These are not the last arrests, with a quite a number still expected," he said.
Asked if more policemen were to be arrested, Ramaloko declined to say.
"The investigation is sensitive. There is a lot evidence still to be recovered," he said.
The three have been charged with being in possession of and dealing in ammunition.
More charges are to be added.