>>4274492all descended from jujitsu, which was developed by the samurai. judo, BJJ and the various other schools of jujitsu all share this history.
they all depend on kuzushi, which in simple terms can be interpreted as using your opponent's energy against them, though this is an oversimplification.
http://en.wikipedia.org/wiki/Kuzushiunfortunately, aikido is really the weakest style in my opinion. it has not proven to be combat effective in the real world. in fact, it's a watered down, weak, mysticised hippy faggot style. mostly consists of deluded fat old men.
"those who esteem chi lack strength".