A few modern campaign questions

[Ricky B]

Hmm, that seems counterintuitive to me. Abandoning means they cut the pontoons loose to drive down river, or destroy their bridging planks, etc. They aren't going to just leave it for the enemy - and it does take a full turn of movement to abandon it, I believe. Doing bridge ops to recover the bridge for later use takes longer as they are carefully collecting the materials for re-use. So it could be considered left in place, but the design was to "destroy" it, at the cost of never building another bridge.

None of it is perfectly simulated, but that is how the design was done, trade offs for any solution at this level, without huge complexities instead, I would imagine.