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By the autumn of 1914, the campaign on the Western Front was bogging down into Trench warfare and there was an urgent need for batteries of heavy and siege artillery to be sent to France. The WO decided that the TF coastal gunners were well enough trained to take over many of the duties in the coastal defences, releasing Regular RGA gunners for service in the field, and 1st line TF RGA companies that had volunteered for overseas service had been authorised to increase their strength by 50 per cent. Although complete defended ports units never went overseas, they did supply trained gunners to RGA units serving overseas. They also provided cadres to form complete units for front line service. The Durham RGA is known to have raised 142nd Heavy Bty and 94th and 149th Siege Btys in 1915–16.