Chain Home (1939)
Britain's first operational radar network: 20 stations along the east and south coasts, transmitting at 20–50 MHz from 100 m towers. They detected German raids while still forming over France, giving Fighter Command the minutes needed to scramble Spitfires. Chain Home Low and Chain Home Extra Low filled the gaps for low-altitude attackers. The network won the Battle of Britain before a shot was fired.
Cold War expansion
After WWII, every NATO member built coastal early-warning radars. The US DEW Line across the Arctic (1957), the Pinetree Line, the Mid-Canada Line — each layer designed to detect Soviet bombers and later missiles. Coastal radars added naval surveillance, fishing-boat tracking and drug-interdiction roles as civilian applications grew.
Modern coastal networks
Today, coastal surveillance blends shore-based radar, AIS ship transponders, unmanned aerial systems and satellite AIS. Systems like Blighter in the UK, CEA in Australia and various ELM-2000 derivatives provide kilometre-scale detection of small boats, drones and low-flying aircraft. The threat is no longer Soviet bombers; it is rubber dinghies with explosives and swarm drones.
Civil-military fusion
Coastal radar data feeds port traffic control, search and rescue, fisheries management and border enforcement. The same sensor network serves multiple agencies. Integration is the challenge — military classification, civilian data sharing laws, and the technical standards that let a coast-guard cutter read a navy radar track in real time.