 Attacks on Royal Navy bases early in the so-called Phoney War period prompted calls for stronger AA defences at Scapa Flow, Invergordon, Rosyth and the Clyde anchorage, and 3rd AA Division was given priority for delivery of HAA guns.The defenders had problems at Scapa, where a chain of rugged islands enclose an extensive area of water, which stretched beyond the reach of HAA fire from the islands.Installing gun positions on the islands required an immense amount of labour.