Bere Island and surrounds were provided with coastal batteries and Martello Towers during the Napoleonic Wars after a failed French landing. By 1850 these fortifications had all been disarmed.
Berehaven Fleet Anchorage was identified as a suitable anchorage for the Royal Navy in 1898 and parts of Bere Island were compulsorily purchased for the building of defences. The sheltered anchorage was more than five miles long and sufficient to shelter a large fleet.
The eastern end of Bere Island, lying to east of what locals call the Red Line, was used by the British forces for three coastal defence batteries, two search light positions, a submarine mining establishment and associated accommodation and buildings. A thinner strip of land on the west shore was used for a further three coastal defence batteries and another searchlight emplacement.
In 1905 the Owens Committee (Home Ports Defence Committee, later the Home Defence Committee) designated Bereheaven as a Class C War Anchorage. The defences around Bere Island were intended to deal with armoured cruisers.
The defences on Bere Island are summarised below:
West Command
- Reenduff Battery built between 1898 and 1903 with two 4.7-inch Q.F. guns
- Derrycreveen Battery built between 1898 and 1903 with two 6-inch Q.F. guns
- Ardnakinna Battery built about 1902 with four 12-pdr QF guns
- Derreycreeveen Defence Electric Light Position with three emplacements
East Command
- Lonehort Battery built between 1898 and 1901 with one 9.2-inch gun Mark X and two 6-inch Q.F. gun
- Rerrin Battery built between 1898 and 1902 with one 9.2-inch gun Mark X and two 6-inch Q.F. gun
- Ardaragh Battery built about 1902 with four 12-pdr QF guns
- Ardaragh East Defence Electric Light Position with four emplacements
- Lonehort Defence Electric Light Position with two emplacements
- Lonehort Observation Post
- A Submarine Mining Establishment at Lawrence Cove
The coastal defences built on Bere Island provide an interesting study because they were all built at the same time on primarily brown field sites. The construction followed the basic Twydal Profile, or dispersal, pattern with earth being the primary building material. Concrete was used for hardened shelters, magazine and gun emplacements.