Police have arrested 29 protesters at a North Yorkshire spy base during a demonstration to mark the first anniversary of the war in Iraq.
Menwith Hill is used by US intelligence services
The protest at Menwith Hill, near Harrogate, is part of the Campaign for Nuclear Disarmament's (CND) continuing opposition to its use by the US.
Officers estimate there were between 130 and 150 people involved.
The arrests were mainly for obstructing the highway or connected with criminal damage.
Protestors started to arrive before dawn with the aim of stopping workers getting in and out of the site.
But the officer in charge of the police operation, Chief Superintendent Bernie Mitchell, said that access to the base had been maintained at all times.
One protestor told BBC Look North: "We might not have been able to have shut down the base for as long as we would have liked.
"But we were able to delay the shift change for three hours.
"We just had a presence here. I think that was important."
Protestors tried to stop access to the base
Among the protesters arrested was campaigning grandmother Lindis Percy.
The 62-year-old, from Hull, was detained for allegedly obstructing a highway, her friend Anni Rainbow said.
Ms Rainbow, a co-ordinator for the Campaign for the Accountability of American Bases (CAAB), said: "She was arrested for allegedly obstructing the highway as she was crossing the road."
Ms Percy sparked a security alert at Buckingham Palace when she climbed the 20ft metal gate in protest against the visit of US President George Bush in November 2003.
North Yorkshire Police said they could not confirm the names of individuals who were arrested at the Menwith Hill protest.
Menwith Hill, on the A50 Harrogate to Skipton road, has a collection of white dome-shaped structures which are believed to contain aerials for intercepting international phone and email and radio traffic.
CND spokesman Neil Kingsworth said they were aiming to show the public the link between the base and war.
"Although no planes ever take off from the Menwith Hill air force base, it is absolutely key to US war-fighting.
"The base is used for advance battle planning, finding targets to hit and monitoring battles as they take place," he claimed.
The protest had been scaled down by early on Friday afternoon but police said they would be continuing to patrol the area.