Objective Lipel 1941 - Newest H2H Approved Scenario!

[Otto von Blotto]

Belarus is predominantly lowland - flat plains occupy 60 percent of the territory, plateaux 10 percent, and highland hilly areas nearly 30 percent. The north-west has broken and highland relief, while in the south-eastern part the land is mainly level. The south of the Republic is occupied by vast areas of Belarusian Polesje (wood land) which is a large waterlogged flat depression stretching for 450 km from the river Bug to the Dniepr.

Might go some way to explain it.