While the development of just when the first ''Wristwatch'' was created is unclear, much of it's origins were based in military need. The standard method of time keeping in the 19th Century was The Pocket Watch. These were circular time pieces that were placed in metal or related cases that could be closed to protect the mechanism inside (normally). The entire device was then carried in the pocket or coat by virtue of a chain attachment.
However during the rigors of Battle, such devices were impracticable. They were much needed though, especially when determining Artillery fire and coordination of troop movements. Navies also used time pieces for many of their course determinations at Sea. Perhaps the first such example of a ''Combat Friendly'' Watch was issued by The German Imperial Navy in the 1880s. But these cumbersome watches were too, impracticable.
By World War I, several European Watchmakers began to design a ''Wristlet'' (as they were called). These time keeping devices were a combination of the Pocket Watch and a ''Modern'' Wristwatch. The Watch featured Face Numerals painted white against a solid black Face. Also, the Second Hand featured a thin coating of Radium ''paint'' which – ''glowed'' in the dark (as result of exposure to any form of low level light sources). This was important due to the need for almost no lighting inside a Trench defensive/offensive position.
Capable of being ''closed'' (as a Pocket Watch), The ''Trench Wristlet'' had (2) metal Threading Bars on either side of the casement, to which a leather or cloth strap could be placed. This could then be tied to the wrist of The Wearer. The popularity of The Trench Wristlet would carry back to ''Civilian Life'', with many Watch Makers modifying the design. By the late 1920s, “Wrist Watches'' would replace the traditional Pocket Watch as the primary source of personal time keeping.