You would be implying that all potential opponents in this world have access/availability to such advance technology .... me guessing.
Concealment is one thing still taught in the military .... especially on tight budgets.

Cheers
Christopher

Good point!
On the other hand, those opponents who do not have that surveillance/detection ability may also lack the ability to do anything aggressive when they do detect the bridge.
Using ones ears is a fairly good way to detect tanks and heavy vehicles. Opponents lacking detection facilities probably also lack the ability to resist suppression of their artillery et.c.
If I was planning on crossing a river or other obstacle which would put my armour in a few chokepoints I would make very sure that there is no enemy artillery or other heavy weapons within striking range.

The decision makers hava made a decision and I believe that there is probably one good military thinker reasonably close to that decision.
/ Robin