Get Amongst Them

Two basic meanings:

1. an instruction to NCOs to go to the Blokes and get them to do something,normally trivial Wombling or Humping and Dumping.

Desperate straights as cavalry break into a square

2. to go to the enemy/whoever and give them a right shoeing. Probably originated from cavalry (actually on a horse) units who once they were in amongst infantry ... well, lets say it was going to get very nasty for the infantry.