When Italy left the war in September 1943, Germany had to provide the occupying forces on its own, severely straining resources in men and material. The Allies also conducted a number of commando raids in the Balkans, including the German-occupied islands of the eastern Mediterranean.
The Axis mounted a series of offensives intended to destroy the Partisans, coming close to doing so in winter and spring of 1943. Despite the setbacks, the Partisans remained a credible fighting force, gaining recognition from the Western Allies and laying the foundations for the post-war Yugoslav state. With support in logistics, equipment, training, and air power from the Western Allies, and Soviet ground troops in the Belgrade Offensive, the Partisans eventually gained control of the entire country and the border regions of Italy and Austria.
German strength as at 5th May 1944 given in a presentation by General Alfred Jodl Chief of OKW Staff:
Finland: no figure given
Denmark: no figure given
The Germans kept a large garrison in northern Italy. Between the Italian attempts at revolt and sabotage and threat of another Allied amphibious attack a fair sized army, albeit of second and third rate soldiers, was kept north of Rome in May 1944. Between incipient revolts practically everywhere and Allied deception operations on all fronts the Germans ended up keeping huge garrisons across the continent.
Note the numbers in the Balkans. German Losses were…
German KIA, Balkans 1941 - 11.30.44: 24,267
German MIA, Balkans 1941 - 11.30.44: 12,060
Compare this with German KIA, Africa Campaign 1940 - 5.43: 12,808
That the Mediterranean Sea has historically always been relevant to the security interests of the leading powers and empires at any time is a well-known fact. Few, if any, Mediterranean countries have had their history so directly dictated by the exigencies of powerful empires concerned with hegemony in the Mediterranean as much as the Maltese islands. Whether as a frontier outpost for the Christian West in its perennial contest with the Muslim East during the period of early modern history—or as the hub of British naval activity in the Mediterranean from the mid-nineteenth century onwards (roughly at the time, 1845, when the building now used as the Malta Maritime Museum was erected as a bakery to supply all the British Mediterranean fleet)—the relevance of Malta to the outside world has been defined by the Mediterranean strategies of others, and the very livelihood of its people accordingly dictated by that fact.