Written by Shin Suk-ju（申 叔舟）in the 15th century
Japanese soldiers prefer to use sword or spear. They forge iron very well to make sword. There is no other sword crafted that well.
朝鮮王朝實録 ‘ The Annals of the Choson Dynasty ‘
'15 May 1487'
Any Japanese swords stored in the arsenal, even lower quality swords are extremely sharp, it's not good idea to sell them because the arms truly reflect Japan's militarism country.
'17 June 1593'
Our swords which bluntness is more like a wooden branch and are a child toy compared to Japanese swords. Our swords are shaved by Japanese swords like hemp.
Written by Ryu Seongryong（柳成龍） in the 16th century
The enemy (Japanese) were foot soldiers. Their swords were as long as 35 to 47 inches with outstanding sharpness. They brandished them left and right swiftly to cut down humans and horses alike. There was no way to repulse their fierce attacks.
Japanese soldiers use swords and spears extremely well. We can not defend against them, because we do not have hard strong durable plate armour. So, we made armour in thick iron, with the intent to charge the Japanese army. However, the iron armour was too heavy to wear.
武藝圖譜通志 ' The Comprehensive Illustrated Manual of Martial Arts in Korea ' in the 18th century.
The Japanese sword is so strong and sharp that the Chinese sword cannot equal it.
The Japanese sword is the strongest and sharpest of sword patterns.
Written by Yi Ik（李瀷）in the 18th century
There are silkworms in our country, but we import raw silk and floss from the suzerain (China). We have iron and furnaces, but our swords and mirrors are no match for the wisdom of Japanese. Our craftsmen compared to other craftsmen around the world are inferior.