The Second World War started as a German agression against Poland in September 1939. At this time, Poland wasn't a democracy, but it was at least an independent and sovereign country.
After WWII, even if Stalin promised to hold fair elections, Poland became a satellite state of the Soviet Union. The 1947 Sejm elections were blatantly rigged by the Communist Party and the Polish Communist Party stayed in power until 1989 without enjoying popular support. Additionally, Poland lost its eastern territories, resulting in massive ethnic cleansing and the deportation of millions of Polish inhabitants.
With a POD after the 22 June 1941, how can you prevent this betrayal? Poland has to stay a sovereign country and hold free elections after WWII.
This requires the Schwarze Kapelle to realize that the war is lost, and their only realistic goal is to limit damage to Germany and moderate the surrender terms. That means they must be a lot cleverer and more rational and realistic than they were. But...
13 March 1943 Operation FLASH succeeds. Hitler is dead.
After some pulling and hauling and maneuvering the SK displace the Nazis. (Goering succeeds as Reichskanzler, Himmler tries to overthrow him, the Army defeats Himmler, Goering is reduced to a figurehead, then forced to step down as he is pretty much discredited anyway...) This takes a few months. It's now summer 1943, the Allies invade Sicily.
The post-Nazi SK tries and fails completely to reach any understanding with the US/UK, then decides to "drive wedges" between the US/UK and the USSR. They approach Stalin, who actually offers a deal - not one they would accept, but evidence of Stalin's bad faith toward his allies. Meanwhile, they propose a truce in Italy, which has surrendered to the Allies and where the Germans are withdrawing to the Alps, and in the air (i.e. no strategic bombing). This truce is to have two purposes: to spare Italy any further combat, and to allow the neo-German regime to transfer all concentration camp prisoners to Allied custody where they can receive proper care, which Germany, bombed and blockaded, cannot provide.
This hammers in a wedge - Stalin will scream bloody murder at such an arrangement, but there will be immense public pressure on the US/UK to save the prisoners. The truce comes into effect in August, Italy is fully liberated. Operations stop till the end of September while trainloads of liberated prisoners pass through the front line in the Alps. When the formal truce is to expire, the front is along an impassable mountain line, and no one sees any point in starting any fighting there; it continues unofficially. The "bomber barons" want to resume hammering Germany, but there's a sense that it may not be necessary - and reports on the effects of Allied bombing (e.g.
Hamburg) are causing second thoughts. The bombing truce also continues.
The Germans also announce the end of all U-boat operations (which is actually a good deal for them - from May 1943 through the end of the war, there were more U-boats lost than Allied freighters sunk). They also reveal Stalin's offer of a separate peace. The US/UK finally break down and start to talk a little to the Germans about surrender conditions.
The neo-Germans, rather ruthlessly, abandon Finland and evacuate Norway (it's no real use to them). They also pull out of Crete, and leave the Dodecanese to be surrendered by the Italians, along with Lesbos and Chios.
Then the Germans drive in another wedge. They contact the Polish government in exile, and offer to reinstate Poland in its pre-war borders (with Danzig as a Free City, final status to be determined by post-war plebiscite). This is a very bitter pill, but -
it will keep the USSR well away from Germany!!! And the General Staff now says that if the war goes on, the Red Flag will inevitably fly over the ruins of Berlin.
The US/UK can hardly object to this, but Stalin does. German forces on the Eastern Front go completely on the defensive, withdrawing carefully to the Dnieper and Luga while making the Soviets pay for every kilometer. The troops withdrawn from Norway and Italy reinforce the East. In November, the Soviets launch a huge two-pronged attack on Kiev. The northern prong is stopped cold at the Dnieper; the southern prong gets 40 km across the Dnieper, and then is cut off and crushed by German counter attacks. A breakthrough south of the Dnieper bend meets a similar fate.
Stalin, in a burst of frustration, orders an all-out attack into Finland, which, sadly, collapses, and Soviet forces occupy northern Norway, stopping north of Narvik when UK forces land there first.
The Teheran Conference in February 1944 is very rancorous. Stalin is angry, petulant, paranoid - accusing the US/UK of betrayal, accusing the Poles of conspiring with "the fascists", defending the crushing of Finland (which has reminded everyone of the Winter War and the Soviet position at that time). Churchill and Roosevelt are not passionately committed to the Polish cause, but they can't just blow it off, and Roosevelt finds that Stalin is not worth making friends with.
There have been peace feelers from Bulgaria, Romania, and Hungary. At Teheran, the Allies agree to accept the surrender of any Axis power, but also define occupation zones for eastern Europe. Bulgaria, Romania, and Hungary are allocated to the USSR, tro placate Stalin. Greece will be restored to its pre-war government (sort of; pre-war strongman Metaxas is dead, and the exiled monarchy has set up in Crete and the Aegean Islands). Albania is allocated to the US and UK. Yugoslavia will also return nominally to its pre-war government, though Tito's Partisans will be included.
The big question is what to do with Germany and Poland. The neo-Germans finally get an answer from the Allies. The only conditions that will be offered are: no dismemberment of the country, no destruction of German industry. The Germans ask for no exclusive Soviet occupation of any part of Germany. Stalin demands an exclusive zone and transit rights across Poland. The Poles object vehemently to the latter.
(Meanwhile, Churchill has been proposing moves into the Balkans while Marshall and the U.S. Army urge accelerating OVERLORD. This bickering pretty much prevents major US/UK action, other than picking up what Germany drops.)
In the end --- German forces peel back from the east, leaving their arms in Poland for the use of the revived Polish state. Polish troops stand at the 1939 border and block Soviet troops from entering Poland. Stalin blusters, but backs down. Soviet troops roll across the Baltic states and continue into Prussia, against weak German resistance (the fortress around Konigsberg holds out).
The USSR occupies Prussia, which becomes an SSR. The USSR also occupies Bulgaria, Romania, and Hungary.
But Poland is spared.