About 100 protesters gathered at a US spy base in Yorkshire as part of an international campaign against the American Missile Defence System.
The base has been the focus of protests for many years
The Campaign for the Accountability of American Bases said it objected to the base's links to the so-called "Star Wars" programme.
Protesters said it was a "dangerous" system which put Menwith Hill at the "front line of any war in space".
The base has been the focus of protests by demonstrators for years.
Lindis Percy, coordinator of the demonstration on Saturday, said the protesters objected to the lack of parliamentary and public scrutiny of the base's link to the US missile defence system.
She said: "This demonstration is going on so that perhaps people just begin to ask some questions about what is going on at Menwith Hill?
"What are they doing? Why haven't we been told, why can't we have a say?"
In a statement, the Ministry of Defence said: "The minor scope of the proposals for RAF Menwith Hill do not raise any planning or environmental issues requiring consultation with local planning authorities."