Here's what I believe happened to start this war between DC and Mortal Kombat. Superman came into outworld searching for Lex Luthur. Lex luthur joins forces with Shao Kahn. Shao Kahn saw Superman and sent Goro after him. Superman flees then went back to Earth to the JLA headquaters. Shao Kahn open a portal to Gothem City, he sent all his army to take over the city. Batman saw the portal and then saw Lex Luthur come out with the army. Right behind Batman, was Sub Zero. Sub Zero thought Batman was Shao Kahn's General. Sub Zero took a swing at Batman, Batman dodge and then took on Sub Zero..........To Be contintued.

Thats my prediction.