The big German push on Stalingrad and points east was originally intended to begin earlier, but finally got underway on June 28, 1942. Ironically, the push towards Stalingrad was primarily a flanking maneuver, intended to provide cover for the main objective of Case Blue (the official name for the offensive), which was the oil fields of the Baku region (in what is now the Republic of Azerbaijan).
The offensive initially proceeded well for the Germans, but unexpectedly strong resistance at Stalingrad (combined with tactical withdrawals by the Soviet Army which allowed in to resupply and find better defensive positions) led to the drive on Baku stalling as Stalingrad consumed the attention and resources of Case Blue’s commanders. In the end, Stalingrad would be the site of one of the bloodiest battles of the entire war, lasting nearly six months altogether, and the site of the first major German defeat on the Eastern front.
Combined with the near simultaneous defeat of the German North African army at El Alamein, the German forces had precious few victories and were steadily pushed back on all fronts.
Broken Heroes — Saxon