Who was Bar-Kochaba?

I was reading NT Wright who mentioned Bar-Kochaba in the book The "Challenge of Jesus." Who was Bar-Kochaba? Was he a false Messiah before Jesus time or was he a Rabbi? And where online can I find more of what he taught since according to NT Wright his teachings shaped 1st century Judeism. I am trying to see things in the light of a first century Jew because it is helping me understand why people acted the way they did during Jesus time. THe way they treated Jesus and the reason why Jesus acted or responded and spoke the way he did. Its been realy helpful in filling in the gaps where things don't translate the message to us in the modern world.