[kolya1]

I should check further but as you can see there are a number a guards units there, among the P-39 units, 9 GIAD, and more particularly 16 GIAP (3rd scoring soviet unit of the war) and 100 GIAP are very famous units.

But the Lavochkin-equipped 5 GIAP was also one of the best fighter units of the VVS (2nd scoring of the war).

I don't know if there is any particular reason for the concentration a P-39 units... Maybe most of them were concentrated in certain VAs in order to simplify the supply system...

Besides, there were several simultaneous major operations at the time, if some units were better than others, they were probably not all concentrated on the same offensive, but this remains speculation...