During World War II, British scientists developed a new and extremely lethal secret weapon: a bomb which released a cloud of sewing needles, tipped with deadly poison.

The weapon is disclosed in the latest release of declassified documents from the UK's National Archive. It was developed at Porton Down, which is now home to Defence Science and Technology Laboratory – but remains notorious for testing chemical and biological weapons on unsuspecting troops during the Cold War. Work on the darts was carried out with the assistance of Canadian and American researchers.

Each dart consisted of a hollow steel needle with a paper tail. The tip of the needle was filled with toxin and a dense 'inertia pellet' above it. When the needle struck a target, the pellet kept going and forced the toxin out of the needle. Breaking the skin was enough to inject a lethal dose.

The needles were tested on sheep and goats under "realistic" conditions, sometimes covered with two layers of clothing and protected by trenches. Researchers concluded that if a needle "penetrat[ed] into the flesh, it will cause death if not plucked out within thirty seconds." Even if the needle was removed, it would cause "cause disablement by collapse."

Media reports (including the BBC) claim that the chemical agent was mustard gas; this is extremely unlikely as the dose required would be much too high. Realistically, it would be one of the new nerve agents that were first fielded during WWII. The lethal dose for Sarin is 30 micrograms per kilogram of body weight, so three milligrams would kill most people. For Mustard gas, the dose needed would be about two hundred times higher. The effects reported on animal subjects (twitching and convulsions followed by death) also strongly suggest a nerve agent.

The program called for the production of thirty million darts. This would require a large number of specially-made needles; the head of the British project contacted the obvious source: the Singer Sewing Machine Company, in a letter apologizing that: "It is a little difficult to explain what I want sewing machine needles for... "

The reply from Singer was helpful, if baffled: "From your remarks it would seem the needles are required for some purpose other than sewing machines. In any case, we should like to help you, if at all possible."

The weapon never went into production, possibly because the darts had very little penetrating power. As soon as its effects were known, scientists said that people would start to take cover under trees or in buildings or vehicles, which would make the rain of darts ineffective. The report also notes that the dart bomb would have been a "highly uneconomical weapon." That may have sealed its fate.

These days, nobody in a western military would dream of using poison darts. But darts filled with a nonlethal "calmative" agent are another matter. British researchers were looking at non-lethal dart gunsfor crowd control back in 1972 ; it wouldn't take much imagination to turn that into a non-lethal artillery round. I wonder if they still have the quote from Singer?

[Picture: British National Archive]

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