The Germans in 1943 found themselves with a very large problem that they had a large western allied force on their southern flank and they a large USSR force to their east. While they weren't near linking up they still both individually posed a large threat to the Germans.
They were forced to both fight on the eastern front, re -establish a government in Italy and conquer the Balkans.
Almost as soon as Mussolini was deposed on 18th July the Germans started preparing to rescue him and once peace between Italy and the Allies occurred within days German units on the 7th September embarked on ambitious rescue mission with troops being dropped by glider almost directly on top of the complex where he was being held and then on ski's escaping before the group a number of days later made it to the coast and at a rendezvous point were picked up by a U- Boat.
Meanwhile in the north of Italy the first German unit of a single Panzer brigade crossed the border on the 10th September and pushed down south through the alpine mountain passes where they encountered no resistance and on the 13th September the Germans reached Verona and pushed through a number of Italian cities encountering no opposition although most citizens remained within their homes and on the 19th September the German brigade entered Rome and Mussolini was reinstalled as the head of the new Italian government.
Even though Rome and all the major cities were now in Axis hands the overall control of the Axis over Italy dropped dramatically with most Italians seeing the new government as nothing more than a Nazis puppet and with the King having gone into hiding into the south a large portion of the population argued the new government was totally illegitimate.
This led to a large amount of resistance from groups which wanted to drive the Nazis out of the country. At first with no enemy forces in the country only 6 German divisions with 2 of them being deployed to the border and for coastal defence so only 4 divisions were left to support the Italian forces under Mussolini.
While the government attempt to raise new forces to defend the country almost as soon as being given arms or in some cases as soon as they received ammunition they simply deserted taking their supplies with them either to join the resistance or to simply defend their home against growing lawlessness and their were examples of men joining up multiple times with one man reported to have signed up for the 22 different times and simply taking his gear deserting and then going onto the next recruitment centre.
Alongside the mass desertions issues the resistance were getting large supplies of weapons sent in by sea and dropped in from the air. The allies happened to have large supplies of captured Italian weapons from North Africa, Albania and Venice although some of the weapons went to new start up militia's in Yugoslavia and Greece still thousands of weapons were flooded into Italy giving them the power to resist.
With this new influx of weapons and willing volunteers the German units found themselves hard pressed and had to abandon all but the cities and even then they had to patrol in force because isolated groups of soldiers smaller than 5 were often found dead in the streets and soldiers were banned from going to any bar not approved due to the rate of drink spiking and soldiers being killed during fraternisation.
Food convoys had to go in large groups and supplies only came in every 2 weeks because all convoys need multiple platoons to escort them and they couldn't get food from local countryside. German attempts at reprisals went poorly with people fleeing the cities and German units were forced to go out into the countryside and destroy abandoned villages.
With the fall of Italy and Yugoslavia's entry into the war the Axis now had a major problem on their southern flank and the Axis planned to take Yugoslavia and Greece but due to heavy troop commitments in Case Blue and Stalingrad couldn't take troops away from Army Group South as Hitler refused point blank to allow any soldiers to be taken away from Caucasus or Stalingrad and so had to remove troops from Army Group Centre whose units would take a long time to reposition and so it was decided that rather than allow the Allies lots of time to dig in they would attack before the end of September on Hitler insistence who saw very little of this force as other than something which was panicking his troops and that local commanders would just have to make do with the units which could be moved in time which was mainly German allied units and reserve forces from Germany itself and only 3 incomplete Panzer divisions and another 2 mechanised divisions which were worn from both fighting and travelling.
On the the 29th September with the entire operation rushed and supplies in disarray while the 5 most experienced and equipped divisions had not had a chance to refit.