Jack and Wang first met when they served together in the military.
- The movie doesn't tell us much about how they first met. The patriotic toast Wang gives at the bar seems out-of-place until you realize that he was saying it only to Jack, not to the entire group. It could be that they first met in the Army or the Navy.
- Unlikely, since Jack never killed a man before the film when he looks horrified after killing a mook before pretending that he does it all the time. Fire-Forged Friends usually get that way by serving in battle together. The events of the film seem to be Jack and Wang's first shared battle.
- Hey, if they were in the Navy rather than the Army they could have seen a lot of combat without ever personally killing anyone — at least, not while close enough to see the person's face.
- It's very possible to serve four years in the Army without seeing combat. Jack having had a "Military Occupation Specialty" (MOS) that was either mechanical or a driver makes the most sense in this scenario. Granted, they're all trained as soldiers first and specialists second, many people in the army don't see combat.