1. “Fall Blau” Objectives: Knock Soviets out of the war
Gain the rich oilfields at Baku
Case Blue later renamed Operation Braunschweig, was the Wehrmacht’s name for its plan for the 1942 strategic summer offensive in southern Russia between 28 June and 24 November The operation was a continuation of the previous year's Operation Barbarossa intended to finally knock the Soviet Union out of the war, and involved a two-pronged attack against the rich oilfields of Baku as well as an advance in the direction of Stalingrad along the Volga River, to cover the flanks of the advance towards Baku.
Initially, the German offensive saw spectacular gains with a rapid advance into the Caucasus capturing vast areas of land and several oil fields.

2. Due to a chaotic Soviet retreat, the Germans were able to advance rapidly, restoring Wehrmacht's confidence for the upcoming major offensive.
Close air support from the Luftwaffe also played an important role in this early success. It contained the Red Air Force, through air superiority operations, and interdiction through attacks on airfields and Soviet defence lines. At times the German air arm acted as a spearhead rather than a support force, ranging on ahead of the tanks and infantry to disrupt and destroy defensive positions. As many as 100 German aircraft were concentrated on a single Soviet division in the path of the spearhead during this phase. Within 26 days, the Soviets lost 783 aircraft compared to a German total of 175

3. Only two weeks into the operation, on 11 July, the Germans began to suffer logistics difficulties, which slowed down the tempo of the advance. The German Sixth Army was continually delayed by fuel shortages. 2 Panzer divisions became stranded during the opening phase. the Luftwaffe's Junkers transport fleet flew in supplies to keep the army going. The situation remained difficult with German troops forced to recover fuel from damaged or abandoned vehicles, and in some cases, leave behind tanks and vehicles with heavy fuel consumption to continue their advance. This undermined the strength of the units, which were forced to leave fighting vehicles behind.

4. Operation Fischreirer
Hitler changed plans and decided to split his army divisions into 2 groups
One was to head towards the Caucuses oil fields (Op. Eidelweiss)
The other was to advance on Stalingrad (Op. Fischreirer)
The advance into Stalingrad against the defenders of the 62nd Army was carried out by the worn out forces of the Sixth Army, while Fourth Panzer Army secured the southern flank. The city itself sprawled in a narrow, 24 km ribbon along the western side of the Volga River, which forced the Germans to conduct a frontal assault against the city, with the ruins of the city heavily favoring the defenders. To deal with the complete air superiority of the Luftwaffe, the commander of the 62nd Army, General Vasily Chuikov, ordered his troops to engage the Germans in close quarters fighting ('hugging' the enemy), rendering the German superiority in combined arms tactics almost useless. TheLuftwaffe nevertheless played a crucial role, as it suppressed Soviet artillery on the eastern bank of the Volga and caused heavy casualties to the Soviet attempts to reinforce the defenders over the river. 

5. 2-pronged counteroffensive against German 6th Army
Operation Uranus
2-pronged counteroffensive against German 6th Army
Hitler, against the advice of most of the involved army commanders, personally ordered Sixth Army to remain on the defensive rather than try to break out. It was intended the Army be re-supplied by air; since the required quantity of supplies was far beyond Luftwaffe delivery capabilities, the fighting strength of Sixth Army diminished and the Soviets gained the upper hand inside the city.

6. Operation Winter Storm
This failed German offensive attempted to strike back at Operation Uranus with the use of the new German “Tiger Tanks”. Over-engineered, these machines often had trouble with their transmissions and were limited in range due to huge fuel consumption. They were created by Austrian-German auto engineer, Ferdinand Porsche.
The offensive gained some ground, but the relief forces never met up with them, resulting in a 3 month long siege that resulted in the destruction of the 6th Army.

7. Operation Little Saturn
Enlarge the area controlled now by the Soviets and push the Germans back to the west
Hitler, against the advice of most of the involved army commanders, personally ordered Sixth Army to remain on the defensive rather than try to break out. It was intended the Army be re-supplied by air; since the required quantity of supplies was far beyond Luftwaffe delivery capabilities, the fighting strength of Sixth Army diminished and the Soviets gained the upper hand inside the city.

8. Overstretched by the vast area they had captured, the reduced capabilities of the Heer and its allies to defend this territory enabled the Soviets to mount a decisive offensive at Stalingrad, encircling a whole German army. Soon both sides concentrated largely on the epic struggle for the city, making the Caucasus campaign a secondary theatre. With Army Group B unable to hold the Volga line, subsequent Soviet operations threatened to cut off Army Group A in the Caucasus, and it was forced to withdraw. The surrender of Sixth Army was a serious blow to German morale in general and it proved a personal shock to Hitler.
The failure of the German Army was nothing short of a disaster. A complete army group was lost at Stalingrad and 91,000 Germans were taken prisoner. With such a massive loss of manpower and equipment, the Germans simply did not have enough manpower to cope with the Russian advance to Germany when it came.
Despite resistance in parts – such as a Kursk – they were in retreat on the Eastern Front from February 1943 on. In his fury, Hitler ordered a day’s national mourning in Germany, not for the men lost at the battle, but for the shame von Paulus had brought on the Wehrmacht and Germany. Paulus was also stripped of his rank to emphasise Hitler’s anger with him.