Early warning

To detect and map enemy planes during World War II, the British Royal Air Force employed a sophisticated network of radar stations, spotters with binoculars, stock market brokers, and a women’s auxiliary with croupier sticks.

Goodchild A (F/O), Royal Air Force official photographer / Public domain

Wars are won and lost on intelligence (see: cryptography gardening). If enemy aircraft are flying over your country, you have to know precisely where they all are – and where they’re going – to mount a successful defence. In World War II Britain, this was the Dowding system. It looked like this:

  1. A curtain of radar stations, known as Chain Home, were installed across the UK coastline to detect incoming planes. Radar was very new at this time, and had never before been operationalised in this way.
  2. Supplementing the radar information were the Royal Observer Corps, volunteers with binoculars who sat in homemade outposts (like garden sheds) and identified planes after they had passed Chain Home and flown inland.
  3. Both the radar stations and the spotters phoned their observations into central “Filter rooms.” There, filterers compiled, correlated, and corrected the torrent of reports coming in. Controllers coordinated with Air Force intelligence about friendly planes in the air and so identified the enemy ones. Because they had to make snap decisions with imprecise and always-changing data, most controllers were recruited from the London Stock Exchange. I imagine that the environment was alarmingly similar.
  4. In order to render the information into a visual and usable form, a giant map was populated with metal markers representing the planes. The plotters, typically from the Women’s Auxiliary Air Force, received information from the filterers and controllers and updated the map with long magnetic croupier sticks.

It was an impressive chain of rapid information gathering, filtering, and sharing, and is widely credited as a cornerstone of the British air defence. It also happens to resemble the world’s largest and most serious tabletop war game. You can see it all in action here:

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