Those are some very unimposing looking rats if I do say so myself.....
Since I've seen how much fun it is to hurl swarms of vicious small animals at enemies with the Murder of Crows Vigour in Bioshock Infinite, I'm all for this idea: it would be a incredibly potent psychological weapon as well. "The Germans use their unholy powers to eat you alive!"
oh they're at peace, that's all. when they go off on the attack their hairs stand on end and their eyes blare and they chirp and squeak real loud too, snapping, clawing, and nibbling away. i've seen lots of rats in my day and they can be quite scary once they start freaking out.
another frightening aspect is that even the rats in your enemy's own trench start attacking them. they're pretty much coming out of everywhere.
this tonic is called "Rattenkonig" it started out in the civilian market to be used by exterminators as they can basically commands rats straight to their deaths without much problem, it was then issued to soldiers to solve their own rat problems in the trenches. but soon the soldiers started using the tonic's rat controlling powers for other purposes.
Ah right, fair enough, can't say I've ever seen real life rats let alone provoked them into biting my fingers off so I'll defer to your judgement on this matter.
Not to mention swarms of vicious small things seems to trigger terror in almost everyone; this would be such an effective trench-sweeper.
That's an interesting idea, to have it start off as a civilian tool that was improvised by Landsers (much in keeping with German military ability to adapt to new situations). What about corpse rats? Could the tonic be modified to create them?
when i was little some of my friends were riding bicycles around the neighborhood, when they saw what appeared to be a large bump on the road, at the end of a block. they didn't care much about it until one of them accidentally ran it over. it wasn't until it was in its death throes that they finally found out it as a rat! it must've been over a foot long!
plus every once in a while my many house cats would kill a large rat. their bodies ripped in half or in bits, and their half eaten skulls. all strewn around the dining hall of all places! some of them were as big as my younger cats.
well of course, corpse rats would be the ideal killer, no modifications to the tonic needed.