By the time Rommel advanced to El Alamein, he already had four German divisions, namely the 15th Panzer Division, the 21st Panzer Division (upgraded from the 5th Light Division), the 90th Light Rapid Division, and the motorized "African Division" consisting of a number of airborne units. But after thousands of kilometers of long-distance desert combat, his "African Panzer Army" has been very badly depleted.
The Germans, with four divisions, had fewer than 40,000 men and more than 100 tanks, and it was normal to lose the Battle of El Alamein, while Rommel's misfortune was that Hitler never realized the importance of the North African battlefield. Major General Rommel, commander of the 7th Panzer Division that swept through Western Europe in the French campaign, took over command of german-Italian forces in North Africa in February 1941 and was promoted to lieutenant general of the German "African Army" to help the Italian allies who had fled in a hurry after being beaten by the British.
In fact, among the first German troops to arrive in North Africa, an armored regiment was missing, because the regiment's tanks sank to the bottom of the Mediterranean Sea with the cargo ships. This was one of the important reasons why Hitler was reluctant to increase Rommel's troops: the route from Italy to North Africa was under the control of the Royal Navy and Air Force for most of the time.
Hitler had a fear of the sea, and he himself admitted that the "Sea Lion Project" that invaded Britain was eventually shelved, and there was more or less a reason for this. The presence of British naval and air forces on the island of Malta, and the weakness of the German Navy's surface combat forces, made any reinforcement operation from mainland Germany to North Africa a dangerous voyage. The lack of tanks, troops, and supplies has always plagued Rommel's tactical play, and in Hitler's view, the limited reserve force of the German army, instead of risking across the sea to reinforce North Africa, it is better to transfuse blood through the railway to the more important Soviet-German battlefield, and everyone will think so.
The German Navy had almost no surface power in the Mediterranean Theater, the escort task of the transport fleet was mainly undertaken by the Italian Navy, and before the initiative in the Soviet-German battlefield changed hands, the decisive force that really assisted Rommel's advance was actually the existence of the 10th Air Force of the Luftwaffe. Based on the Italian Airfields, they completely suppressed the Royal Navy and Air Force of Malta, smoothing the Mediterranean route for a while while also covering the rapid advance of Rommel's ground forces.
With the Soviet-German battlefield tightening and the main force of the 10th Air Force transferred out in the second half of 1942, The British fighters and the Mediterranean Fleet in Malta could be described as a resurgence, violently attacking all the past Axis fleets, and Rommel's good days were over. The German armored units, which lacked air cover, also suffered heavy losses under the overwhelming superiority of the Royal Air Force, so Rommel lacked not only reinforcements and tanks, but also the exhaustion of the Luftwaffe was the second important reason.
Was Hitler unable to give Rommel some necessary assistance, then? Apparently not, in May 1943, after Rommel was sent back to recuperate, the Tunisian campaign was completely over, and the remnants of the German-Italian army of 250,000 people entered the prisoner-of-war camp, of which the German 5th Panzer Army (renamed the African Panzer Army) under the command of General Arnim alone had seven divisions, including the 10th Panzer Division and the Waffen-SS units, and the number of captured was as high as 125,000. That is, in the final stages of the North African battlefield, Hitler still had the ability to urgently carry out reinforcements, the problem was too late!
History cannot be repeated, but if Rommel had had seven German divisions and enough tanks at the Battle of El Alamein a year earlier, Montgomery would almost certainly have been defeated, and the Germans would have rushed to the Nile to completely occupy Egypt, and then swept north through the Oil-producing regions of the Middle East, southwards to India to meet the Japanese, and even detoured to the Caucasus to meet the Soviet-German "Army Group South".
It would have been a very frightening situation, and the situation that the Joint Committee of Chiefs of Staff of the United States and Britain feared the most, but none of this had happened, for Rommel's Afrika Korps were already extremely weak and strong.
Ultimately, the third most important reason is that Hitler's global strategic landscape is still insufficient, and Germany's strategic resources are really insufficient. Before Rommel went to the North African theater, Hitler had no intention of opening up a battlefield in Africa, and the original plan was to use these valuable troops in the Balkans. However, if Mussolini is not helped, the "indisputable ally", then the Axis Group may split or Mussolini cross the stage. How to say it? Just as he passively intervened in the Spanish Civil War, Pelommel's conquest of North Africa was Hitler's reluctant choice, an involuntary combat operation.
Hitler thought the most about the presence of the Rommel Legion to stabilize Mussolini's regime and, once a limited victory in the non-North African theater, could also deal a heavy blow and contain British power, and nothing more. As for the strategic goal of going deep into the Middle East and roundabout the Caucasus, he did not even think about it. He did not even expect that Rommel would achieve such great success with such a limited number of troops that the German Army General Staff and the Italian General Staff initially gave Rommel the task of simply defending Libya so as not to let the Italian army collapse, and they even prevented the Afrika Korps from attacking the east indefinitely.
Even in the Tunisian campaign of surprise reinforcements, Hitler's goal was only to prevent the total collapse of the North African battlefield, so that the Allies would inevitably land on Italy in the next step, so the Germans were still a temporary action of "headache and foot pain". As a result, because the sea route was tightly sealed, the seven elite German divisions eventually had no way to retreat and the entire army was destroyed. Wouldn't it have been better if Arnim's 5th Panzer Army had not made such a senseless sacrifice and simply thrown itself into the Soviet-German battlefield, which was short of troops?
When Rommel asked for reinforcements in 1942, Hitler sent only a medal and the field marshal's staff, which could not frighten Montgomery, and the victory or defeat of the war depended on strength.