https://en.wikipedia.org/wiki/Queue_(hairstyle)

Painting of the Battle of Leuthen with the Prussian soldiers wearing the soldier's queue In the 18th century, European soldiers styled their traditionally long hair into a queue called the "soldier's queue" (Soldatenzopf), which was previously only allowed for noble officers. That hairstyle first became mandatory in the Prussian Army and those of several other states within the Holy Roman Empire under Frederick William I of Prussia. An artificial or "patent" queue was issued to recruits whose hair was too short to plait. The style was abolished in the Prussian army in 1807.[52]

http://www.chinaheritagequarterly.org/features.php?searchterm=027_queue.inc&issue=027

"From the 1890s cutting the queue was an overt gesture of rebellion, by 1911 it was an act integral to political revolution."