You do realize (wait, you and some others probably don’t) that the Russians have anticipated such occurrences given they will and are building pontoon bridges to circumvent?
Not there they won’t. Fast current and width preclude any pontoon bridge which, by the way, is easily taken out - even if the Russians were any good at making pontoon bridges, let alone long span ones.
Pontoon bridges are themselves evenore vulnerable, and can’t carry the same weight of traffic.
They will then just hit the pontoon bridge. EZPEEZE
The Russians haven’t even been able to bridge creeks and swamps the last few months. How in the world do you expect them to span a kilometer wide stretch of river with pontoon boats?
And your idea of them using fairies is fanciful because that could work for small amounts of supplies and for small numbers of troops. But they’re not gonna get heavy equipment across that river in small boats.