Before the battle
After the Battle of Kursk Wehrmacht had lost all hope for a decisive victory over the Soviet Union. The losses were considerable, and, worse, the army as a whole was much less experienced than before, because many of its best fighters died in previous battles. As a result, despite the significant forces, the Wehrmacht could really only rely on tactical success in a long defense of their positions on the Soviet troops. German offensive from time to time to produce significant results, but to translate them into strategic victory to the Germans could not.
By mid-August, Hitler realized that the Soviet offensive will not stop - at least for as long as the ranks of the allies will not be reached. Therefore, his solution was to buy time through the construction of numerous fortifications to contain the Red Army. He demanded that the Wehrmacht soldiers defended positions on the Dnieper at any price.
On the other hand, Stalin was determined to force the return of captured territories. The greatest importance in this respect was represented by industrial regions of Ukraine, and because of the extremely high population density, and because of the concentration there of coal and other deposits that would provide the Soviet state since he lacks the resources. Thus, the southbound became the main direction of attack by Soviet forces, even at the expense of a northern front.