I can't answer this question directly, but military uniforms for much of history have had a fairly strong influence on fashion - the practice of men wearing wristwatches, for instance, comes from WWI. Previously, wristwatches were considered womanswear, and the only men who would wear them were soldiers, who liked the practicality. After WWI, people began wearing them because they were seen as manly, and to signify they had been fighting - or at least to create that impression even if they hadn't - and thus get respect.

That's just one example - there are plenty of others though: Aviators are a WWII design, neckties apparently began with Croat mercenaries, trench coats...you guessed it. Here's a master's thesis I found with Google, which looks interesting.