Strategically, if the Allies want to defeat Germany quickly and steadily, they must make full use of their huge advantages in military strength, open up a lot of battlefields to lengthen the German front, so that the German troops are more dispersed, and eventually lose the initiative, when the huge ground forces of the British and American allies are almost idle, only one Italian battlefield is too narrow, can not accommodate too many Allied troops, and Italy is mostly mountainous terrain, easy to defend, the German army can use less troops to stop the Allied attack, Coupled with the fact that the Allied offensive in Italy appeared to be more cautious, the War in Italy eventually reached a stalemate, and the Allies only contained more than 20 German divisions, apparently failing to achieve a greater impact, and the Allies needed to open up new battlefields to invest their huge army and annihilate or contain more German troops.
From a military point of view, Italy is a long and narrow peninsula, and the terrain is complex, and ground operations are beneficial to the defensive side, that is to say, to the German army. At that time, the reason for choosing Italy for landing was because of the huge victory of the Allies in the North African battlefield, in the final Tunisian campaign, the Allies completely annihilated the entire Axis African Army Group, the mediterranean battlefield situation was extremely favorable to the Allies, there were few German troops in Italy, and the Italian army was also demoralized and had no will to fight, the Allies believed that Italy at this time had opened its doors and had no defense, and it was very likely that the amphibious landing from here would be successful, and then force Italy to withdraw from the battlefield. Ending the military alliance with Germany, the Allies envisioned that the Italian army would collapse rapidly, and the German army would not have time to enter Italy to establish a defensive line, and the Allies could quickly occupy all of Italy and march into the heart of Europe. It has to be said that the Allies' judgment of the situation is very accurate, and if their military operations are faster and the battle plan is not so conservative, perhaps the Allies will really succeed.
As a practical result, the Allies failed to make effective use of their superior naval and air power to exploit italy's special terrain of three seas to carry out extensive amphibious landings to bypass the German rear, but instead took advantage of the frontal advance of ground forces, failing to take advantage of the victory in the Battle of Tunis to rapidly expand, and the Germans had rebuilt the Italian defense line and launched a long-term defense. Several large-scale allied offensives, with very limited progress and heavy losses, the Italian battlefield has lost its original significance, reduced to a secondary battlefield, the Allies must seek a wider ground battlefield to accommodate their army, landing in France is imperative.
From the Soviet point of view, the Allies must also step up the opening of new battlefields, and the Western Allies have promised the Soviet Union from 1942 to open a new ground front to contain no less than 40 German divisions, thus greatly alleviating the huge pressure on the Soviet army on the Eastern Front. The opening of the Italian battlefield was obviously not satisfactory to Stalin, where only the strength of the 23 german divisions was contained, of which only 15 divisions were on the front line, which was only equivalent to the strength of a German army group, and the impact on the German army on the eastern front was really not worth mentioning. Stalin would never tolerate his army's bloody sacrifice while his Western allies stayed idle on British soil, so Stalin has been asking the Allies to open up new battlefields as soon as possible and launch a landing on the European continent!