The First World War drove this point home. The United States sent its troops to Europe. They found, on arriving, that Europeans used different weapons, had a different sizing system for uniforms, and measured distance differently. They also found that there wasn’t much they could do about it. The U.S. Army was fighting an away game, so it made uncomfortable adjustments. It switched over to the metric system for the war’s duration, manufacturing metric provisions, issuing metric maps, and giving its orders in metric units. Fighting in kilometers and kilograms wasn’t easy for men who’d grown up
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