 During the Battle of Britain, Anti-Aircraft (AA) defence for the area was the responsibility of the Harwich Gun Defence Area (GDA), manned by 99th (London Welsh) Heavy Anti-Aircraft Regiment, Royal Artillery.The GDA's main focus was on the Port of Harwich, and in July 1940 there were almost daily attacks on shipping off the East Coast, but 302 Heavy AA Battery also had a detachment stationed at Martlesham.The "Luftwaffe" began its offensive against RAF Fighter Command airfields in August.