How many movies have Yang Dong-Wuk and Yu Chang-Guk collaborated on?

They have worked on 4 movies together! Their first movie together was Thunderhawk From Outer Space (1986) while their highest rated movie together was Thunderhawk 3 - Thunderhawk From Outer Space Blitzkrieg (1987). They have not worked together since Super Hong Gil-Dong (1988). They are most known for their family films together.