Cosplay, or costume play, the art of dressing up and acting the role of (usually) a historical or fantasy character has become immensely popular. Many people think that it is a recent phenomenon, but the tradition goes all the way back to the 1930's, when fans at early science-fiction conventions dressed up in space suits and futuristic garb. Even Forrest J Ackerman was known to show his enthusiasm by wearing his own sci-fi outfit at these events.
The term Cosplay was coined in 1984 by Nobuyuki Takahashi, a Japanese film producer after visiting a Worldcon Convention in Los Angeles and seeing a multitude of fans wearing costumes of their favorite superheroes and anime characters. The name stuck and it's been used ever since to describe this activity.
One of the threads of this sub-culture is fantasy cosplay, and in this case, women who dress up as warriors. Perhaps partially inspired by the Vikings TV series, many of these costumes appear to be influenced by that period of history. Another group of women don a more modern version, complete with camouflage outfits and military weaponry. While this may seem outwardly exploitative, it allows the participates to harness their personal power and express it in ways that they may not be able to achieve in their normal lives.
Here are a few examples found from around the 'net.