Police from five forces have carried out raids aimed at stopping an escalating feud in the travelling community which saw two teenagers' skulls being dug up and stolen from a grave.
Some 150 officers were involved in the operation led by Durham Police and which also involved Cleveland, Northumbria, North Yorkshire and South Yorkshire forces.
Officers in protective gear raided a number of sites across Northern England and recovered firearms and vehicles.
The major operation was designed to bring a halt to an ongoing feud between travellers which has seen homes attacked in recent months.
A house in Darlington was petrol-bombed and in the last fortnight a bungalow was wrecked when a horse box was driven into it deliberately.
Days later another address in the town was smashed when a stolen recovery truck was driven into it.
Events took a macabre turn at the weekend when it was discovered a grave in the quiet hamlet of Metal Bridge had been desecrated.
In an act which seasoned detectives called "depraved", the skulls of brothers Levi George Price and Gareth Price, who were both 16 when they died in 2001 and 2005 respectively, were stolen.
They have not been recovered.
The graveyard attack was firmly linked with the ongoing feud, Detective Superintendent Adrian Green said.
Speaking this week about the cemetery disturbance, he said: "This has taken things too far. It is depraved and goes against the religious and cultural beliefs of decent people."
Gareth Price was found hanging at Lancaster Farms Young Offenders Insitution in 2005, the day before he was due to be sentenced for rape.
An inquest found he had been let down by a series of people in authority.
Levi Price was found hanging in a shed in 2001. The coroner found he could not be sure the teenager intended to kill himself.
Chief Inspector Caroline Dawson said the theft of the skulls was "despicable" and a crime which shocked the travelling community.
She said the operation was not designed to target them as a whole, but a small group within that community.
"Hopefully, this will get us a crucial piece of information we need to be able to repatriate the missing skulls," she said.
Police said on Wednesday that four people have been charged with conspiracy to commit GBH.
Police said operations were carried out in Doncaster, York, Middlesbrough, West Rainton in County Durham, and near the Baltic Centre in Gateshead. A number of arrests have been made.