http://en.wikipedia.org/wiki/Sengoku_period
Japan was constantly fighting themselves. And they weren't always secluded.
They weren't always ruled by an "Emperor" either. or at least, the emperor wasn't always important. See "FEUDAL LORD."
most of the samurai were trained in the basic samurai technique and in the basic way to hold a sword.
KENDO is the name of the samurai sword technique I think. What the fuck is wrong with you? You think just because they weren't associating with the outside world means that they wouldn't have developed their own sword techniques? Stupid.
this conversation is pointless because you're either an idiot or you're acting like an idiot. Go play a samurai fighting videogame or something.