The shipyard at the heart of the British Royal Navy's headquarters is to close, leading to the loss of hundreds of jobs and the end of 500 years of military shipbuilding tradition.
British defence contractor BAE Systems said on Wednesday it would end all shipbuilding in Portmouth from next year.
The decision, which marks the end of over 500 years of work in Portsmouth, will also involve BAE consolidating its
operations in Glasgow, where it has two sites in Govan and Scotstoun.
If Scotland votes to become independent next year in a planned referrendum, it would mean England - which forged the British empire via control of the seas - will no longer have a capacity to build its own naval forces.
The cuts will affect 940 workers in Portsmouth in 2014, as well as 835 at Filton, in south-west England, and Glasgow and Rosyth in Scotland through to 2016, BAE said.
"Following detailed discussions about how best to sustain the long-term capability to deliver complex warships, BAE Systems has agreed with the UK Ministry of Defence that Glasgow would be the most effective location for the manufacture of the future Type 26 ships," it said on Wednesday.
"Under these proposals, shipbuilding operations at Portsmouth will cease in the second half of 2014," it said.
The cost of the restructuring would be borne by the MoD, it said.