Ah, fashion!

In 1388, the Good Duke (Louis of Bourbon) was campaigning on the German frontier. As he besieged a castle, one of the duke's servants, a valet of the wine cellar, offered to arrange an infiltration of the fortress. The valet was from that part of Germany, and he figured that he could talk himself and a small company into the castle. Part of his confidence came from the current fashion:

So everyone in the household Duke of Bourbon said that it was a good strategy of war, seeing that in this time everyone was dressed like a German anyway.

I love the Chronicle of the Good Duke.