The Island of Hoy was very important during the War. There were numerous military installations and vast amounts of infrastructure to support them.

Two Gun Batteries were located on Hoy itself with a further one on South Walls.

There was a major Naval Base at Lyness complete with harbour, oil tanks, pumping station etc. There was a Major base at Rinnigill and the main communications centre for Scapa Flow at Wee Fea. There were also barrage balloon stations and heavy anti aircraft batteries with gun aiming radar throughout the Island.

Many remains are to be found today, even such things as Anderson Shelters are still extant, with many of them having found new uses.