Manstein was fully aware of the terms on which the winter battles would have to be fought. The long-standing strategic threat to the Army Group South left flank was stronger than ever. It could take the form of a deep envelopment carried west to the Carpathians or a shorter southward thrust between the Dnepr and the Dnestr. In his order to Fourth Panzer Army Manstein chose to concentrate on defending against the southward thrust as the most immediately dangerous and the one on which Vatutin appeared to be concentrating.
Additionally, since the front had moved back to the Dnepr a new menace had come to the fore. It was the threat to the army group's lifelines, the railroads. They were
two: on the north the line Lublin-Kovel'-Shepetovka-Berdichev-Kazatin and about fifty miles farther south the roughly parallel line L'vov-Ternopol-Proskurov-Zhmerinka. If they were cut, all of the Army Groups South and A supplies would have to be rerouted over the Rumanian railroads, which were in dismal condition and were certain to become worse as the front drew closer to the Rumanian border.