Centuries ago, during Japanese feudal periods, people used swords as weapons. In battlefields, they were secondary weapons when spears and bows were no longer applicable for close range battles. Forging them took sometime and they were considered as sacred artwork. These deadly works of art were used to defend or as a killing devices.
At the end of world war II, carrying these deadly weapons was banned. Swords were considered as deadly weapons and were destroyed while those with high artistic value could be owned and preserved.
Nowadays we see them in movies moving gracefully with dangerous stunts, in martial arts competitions, in news and here in Deviantart.
These are some of the deviants posing in deadly blades: