Isolation question

[Green]

The two Russian units are not on a supply source. But if the Germans units were not present the Russians units could trace a supply line on their side of the river. The river shown is the Dnepr, roughly 70 kms west of Smolensk. Russians on both sides of the river will generally be able to trace a line of supply unless German units prevent it.

So it is the Germans that will cause the isolation, not the blown bridge by itself . Some or all of the German units shown presumably moved to their locations during the current turn. Once the turn is ended, the Russian units in question will be Isolated at the start of their turn.