A trench knife is brass knuckles with a blade, I do believe.
In the Air Force, the saying “the balloon goes up” was used in place of “if the shit hits the fan” or something similar. I always took the “balloon” to be a nuke fireball but instead it traces back to World War One.
When enemy observation balloons went up, it usually signalled imminent enemy artillery and subsequent attack. In the Second World War, barrage balloons were hoisted to ward off dive bombers, who feared damage from the steel cables attached to the balloons.
Bottom line ... nothing good happens when the balloon goes up.
Duly noted and thanks.