A Time for War
Hands-free, accurate timepieces became crucial for the more-mobile soldiers of the 20th century. At first, guys would improvise with leather straps that were cupped to fit their pocket watches, but if you've ever seen a pocket watch, you can imagine how big a guy's wrist would have to be to call that even remotely useful. Watchmakers like Girard-Perregeaux started equipping soldiers and sailors around the turn of the century, which meant attacks and troop movement could now be coordinated. Pierced metal shrapnel guards were fitted over the crystal faces, and eventually radium was painted onto the hands so soldiers could tell time in the dark and make up phrases like "oh-dark-thirty."