This is a Korean-made film largely set in Manchuria during the 1930s, a period when that territory was under Japanese occupation. The film follows three rival Korean gunslingers (broadly modelled on the characters played by Clint Eastwood, Lee Van Cleef*, and Eli Wallach in the famous Sergio Leone film) as they fight against each other and various other actors (including nomadic warriors, urban gangs, sinister criminals, and the Japanese army) to locate a map that holds the key to the location of unspecified riches. It features a number of incredible set pieces, of which the multi-factioned shoot out on a train at the start sets the scene. The Mad Max style chase that comes just before the three-way shoot out is also rather impressive. So I recommend this highly, if you like fun.
*Though in this film, it is like they got a Korean analogue of Prince in to play that role.