Today I learned about manyf Korean war.  I was deeply impressed two things.

First, I want tell about sal -su river.Eul-ju-moon-deok built dam and when the Wo-Jong-moon and soliders reached the half of sal-su river Eul-ju-moon-deok open tne dam and many Sui china's people died.  just 2,700 people survived.

That was one of 3 greatest victors in Korean war history.

I have 2nd story bong su. The Joseon people used smoke to communication. There was any commucation thing like telephone. They just use walk or smoke. Bong su is the smoke and fire signer. It looks like chimney, there are signer,  very effective way to keep our border.

   1 smoke  : nomal condition.

   2 smoke  : enemy is peeparing for war

   3 smoke  : the enemey is near the border

   4 smoke  : the enemey cross the border

   5 smoke  : It is time to fight