According to Why Hasn't the U.S. Gone Metric?:

In the 1970s, some opponents suggested that metric road signs would facilitate a Russian invasion.

This ("... some opponents suggested...") sounds very likely, but it's true?

The exhaustive report A History of the Metric System Controversy in the United States was published in 1971...

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    Russia is mentioned in the exhaustive report several times, not as a potential invader but in reference to its metrication history (along with other countries). The first link refers to "English" units (we call them imperial units) and claims the gallon standard was held in London, which I don't believe because the US gallon isn't the same volume as the imperial gallon, and so I don't rate it with much credibility, nor its unsubstantiated claim that "some opponents suggested that metric road signs would facilitate a Russian invasion." It makes sense as a comedy gag, not as a serious argument. Jul 3, 2020 at 16:58
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    Back when there was a push to make US road mileage indicators use metric units (which I'm thinking was the late 60s - early 70s) there was a fairly strong conspiracy theory going around that this was somehow a "Communist" thing. And I suspect that was a major reason for the failure of the effort. Jul 3, 2020 at 17:12
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    And here is an entertaining 1977 interview of metric opponent Dean Krakel by Canada's CBC. Again, lots of communism-related objections, but no specific mention of invasions. Jul 3, 2020 at 17:30
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    This question can pretty much only be answered in one direction. Demonstrating that no-one made the claim will be infeasible.
    – Oddthinking
    Jul 4, 2020 at 18:29
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    In the US there is almost certainly at least one person who suggested that any conspiracy theory is true. Jul 4, 2020 at 22:24

1 Answer 1


Latest date and not the same claim, but... quote from Meet the Sole Employee of the U.S. Metric Program:

As the years went on, the Metric system wasn't only derided as confusing. It was a communist conspiracy! If the Americans converted under a multi-million dollar price tag, it was prime time for the Soviets to invade our weakened economy, according to the author of the 1981 book Metric Madness: Over 150 Reasons for NOT Converting to the Metric System.

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