That isn't really discussed until a few more tablets, it was mentioned briefly in the previous tablet, but in this one, the nuclear missiles are used in order to make a path through the Hammered Bracelet. Although, the way Nibiru bashes into Tiamat, it kind of is described as if two massive bodies are going to war with advanced weaponry. I need to look into the Enuma Elish myself where it is told in full.