Notes:

Oh, for anyone curious, 50% casualties renders a unit operationally ineffective and at that point, any sane commander would withdraw them from the front.

The general answer to how one should force an armoured spearhead over a river not shallow or slow enough to ford without a pontoon bridge into unknown hostile territory where the enemy is known to have high-quality reconnaissance and heavy fire support is that you don't; but if you must, calling it a day after losing 20% is generally advised, as anymore then that, you won't be able to effectively fend of an enemy counter attack whilst also simultaneously trying to establish a bridge head.

So in short, an ex-artillery commander probably isn't the best one to listen to in regards to armoured or infantry warfare.