If I understand it right, CNN first reported that pontoon bridge this Tuesday, May 10, from open source intelligence. On Wednesday, May 11, Ukraine hit it with artillery. One battalion's worth of men and equipment were wiped out. Estimated losses were 100 vehicles destroyed and 1,000 to 1,500 men dead. They were bunched up while crossing the river and could not get out of the way fast enough, which means artillery caused a lot destruction and casualties fast.
Russia ignored that Ukraine knew where that bridge was. They tried to cross it anyway, when by now they have to know good Ukraine is using drone targeted artillery. Conducting a operation when the enemy knows it is coming happens in war. That is not what I do not understand.
What I do not understand is Russia took no means to protect their own operation. As far as I know, there was no air cover attempting to suppress artillery, and no counter battery fire. Russia seems to be oblivious to how Ukraine is fighting back or what their own operating limits are.
Go ahead and call me naive, I do not understand how Russia's army let this happen.
You are correct that the Russians did just about everything wrong you can do in trying to launch an attack across a river. They should have read their basic training manuals more carefully.
I think we may be seeing the results of poor organization, weak communications technology, and a dramatically incorrect assessment of the opponents ability and forces. A lot of recent military experience by US, Russian, and NATO forces has been against vastly weaker forces. Just like the US and others appeared to underestimate the Ukrainian military before the war the Russians did too. And they are suffering the consequences.
Here's one particular analysis that you might find interesting.
Its veracity is up for debate, but that particular river was apparently crossed in numerous other areas beyond the spot where those were photos taken, based on fighting reports elsewhere (and acknowledgement that Russians have established positions west of the river):
This river goes all over the place in the Donbass:
