ANTI INVASION DEFENCE SITE

SN Sites, buildings and structures associated with the defence of the British Isles against invasion from seaborne or airborne forces.
CL MILITARY DEFENCE AND FORTIFICATION
BT DEFENCE SITE
NT ANTI BOAT LANDING OBSTACLE
ANTI LANDING OBSTACLE
ANTI SUBMARINE DEFENCE
ANTI TANK ISLAND
ANTI TANK OBSTACLE
AUXILIARY UNIT SITE
BARBED WIRE ENTANGLEMENT
BUNKER
CENTRE OF RESISTANCE
CHECKPOINT
DEFENDED LOCALITY
DEMOLITION CHARGE SITE
FIELDWORK
GUN EMPLACEMENT
LYON LIGHT EMPLACEMENT
PETROLEUM WARFARE SITE
PILLBOX
RAILBLOCK
ROADBLOCK
SPIGOT MORTAR EMPLACEMENT
STOP LINE
VULNERABLE DEFILE