The all-time most-watched film in South Korea. 17.6 million tickets were sold nationwide.
The set pieces, costumes, weapons, and more were all designed and constructed after extensive research. For example, the crew designed a Japanese warship that was so realistic, when they sent it to a historical museum in Japan for confirmation, the historians there were in awe.
Only 8 ships were built for the film--the rest were constructed by CG.
Many extras who wore armor in the film suffered neck pain.
For the obvious modern political reasons, Ming wasn't mentioned for once in the whole movie. Movie paints picture that it was Joseon alone in the face against superior invading Japanese force. In reality it was massive Ming military help which saved Joseon from completely being overrun by invading Japanese forces. Furthermore, Yi Sun-sin was so highly regarded by Ming generals that he received the dou du (commander-in-chief) title from the Chinese court.