More than 20 activists set up camp outside the AWE in Burghfield, Berkshire, at 2am, pitching their tents under cover of darkness for a fortnight of protest.
Organisers Trident Ploughshares and Action AWE said they wanted politicians to support Britain's disarmament obligations under the nuclear Non-Proliferation Treaty and join multilateral efforts to ban nuclear weapons worldwide.
It's the latest in a campaign of action to highlight the lunacy of nuclear weapons across England and Scotland.
Activists are planning a blockade of the site on September 2.
Andreas Speck of Action AWE told the Star that as of today afternoon they had not been threatened with arrest and that the protesters were determined to remain at the site.
"We had approached the MoD and the police to ask for a site for the camp but they refused so we just took the land," he said.
He said the camp aimed to "build up the pressure on MPs to take a position" on Trident renewal, which is set to be made in the next parliament.
He urged the public to write to their MPs expressing their opposition to Trident but also to engage in non-violent direct action.
"They must believe that they can make a difference, not just leave it to the politicians," he said.