Game mechanism : plan an offensive

[burroughs]

If You play with the vanilla 3.4 version then brace yourself for more of such nasty surprises.

Besides You apparently ordered an all-out assault from a single direction along a single axis of advance, no flanking and on a narrow front from a river hex with swampy terrain - I am not sure, I use the old classic map layout, it's more readable for me or I have just grown accustomed to - with units that apparently use mixed movement mode - or motorized / tracked - at best against a fortified location with a unit of up to a divisional strength, augmented with static artillery assets. I guess You must have heard about the WWI experiences with such ideas? At best it's something that happened at Cambrai, but they had much wider front there in operation GY and yet it was a doomed enterprise falling short of void victory. Finally, two of those regiments are in not so good condition regarding their supply levels, the rest just a scratch better and only the infantry division is fairly supplied, but then they were allowed only minimal effort.

I'd say I am not surprised at all with the result. You're quite lucky nothing's evaporated / relocated to the rear to be rebuilt.