RAF Bomber Command blinded German radar with foil strips

By 1943 German night-fighter defenses, built around the radar-guided Kammhuber Line, had made RAF bombing raids over Germany increasingly costly — no amount of evasive flying or aircraft redesign changed the fact that a radar set could detect and track a metal aircraft reliably at range. British researcher Joan Curran had already worked out, years earlier, that cutting aluminum strips to roughly half the wavelength of German radar and releasing them in bulk from an aircraft would flood radar screens with reflective false echoes indistinguishable from real bombers.

The countermeasure sat unused for years for a reason that had nothing to do with whether it worked: British leadership knew Germany had independently discovered the same principle, and using it first meant handing the Luftwaffe a tool that could just as easily blind Britain's own radar-based air defense during a German raid — a standoff where neither side wanted to be the one to open a door neither could then close.

Flooded the radar with false returns: bombers dropped aluminum strips cut to radar wavelength, creating indistinguishable echoes that swamped the real stream.

Aluminum strips cut to radar wavelength reflected as strongly as bombers, creating indistinguishable false returns.

Releasing thousands per minute flooded screens with more false echoes than real aircraft, overwhelming operators.

Radar's vulnerability was not sensitivity but discrimination, so flooding made detection useless regardless of technology.

The tactic was held back because both sides knew it, but Britain used it first when offensive gain outweighed defensive risk.

When a detection system can't be evaded, overwhelm it with cheap, plausible false signals that break its ability to discriminate.

On the raid's first night German radar-guided night fighters and anti-aircraft guns were left firing into empty sky, and RAF losses fell to roughly 12 aircraft against a typical toll closer to 50 for a raid of that scale; across the full Hamburg campaign the Luftwaffe was forced to abandon its rigid Kammhuber Line system entirely in favor of looser, less radar-dependent fighter tactics.