Workers at the Faslane nuclear naval base in Scotland are to stage a two-hour strike next week followed by further walkouts, in a row over pay.
Unite said hundreds of its members at the base, and at another site in Coulport, also on the Clyde, will walk out at 10am on February 19.
There will also be a number of "staged stoppages" from February 20 onwards.
It will be the first time workers at the bases have been on strike for 42 years.
A work to rule, call-out ban and a ban on all non-contractual overtime will also start on February 19.
Unite said the action was in protest at a below-inflation 1% pay rise imposed by employers Babcock Marine.
Unite national officer Ian Waddell said: "The first mass industrial action on the Clyde in 42 years should set alarm bells ringing in the MoD and really crystallise the problems created by Babcock's refusal to negotiate a consolidated pay deal which it can more than afford."
"Babcock continues to bury its head in the sand by refusing our conciliation proposals and stonewalling our calls for evidence on the nature of its contract with the MoD.
"A prolonged period of industrial action will severely disrupt day-to-day operations at the Faslane and Coulport base, but the workers will strive to ensure the safety of the workforce, the naval base and the local communities will not be compromised.
"Over 800 workers across all aspects of the Clyde's operations have spoken collectively - they want a fair deal on pay and they want the company to negotiate with their trade union, Unite, to achieve this."