This raises all sorts of possibilities and is the Soviet Union's bête noire. Here we have the primary result of the end of the Second World War and the development of the Cold War turned on its head: A reunified and rearmed Germany occupying Poland and the Soviet Union being blackmailed into allowing it to keep Western Poland or face annihilation by American nuclear weapons.
Would the Soviets accept a German occupation of Western Poland and believe that NATO could restrain the Germans from attacking Russia in the future? I doubt it.
Why? Because the Soviets were paranoid in the extreme about German unification and the German military and with very good reason.
They won the Second World War but at huge cost. If America and Britain had not also been fighting against Germany would the Soviets have beaten Germany by themselves? Who knows.
During the Cold War the Soviet Union placed the largest concentration of its land and air forces outside of the Soviet Union in East Germany, and placed them there to fight West Germany.
The Soviet Union would not allow East Germany to develop an arms industry during the Cold War, despite the fact that East Germany was the Soviet Union's most reliable ally in the Warsaw Pact and that the East German Army was the only "allied "army that the Red Army actually trusted. And of course elements of the East German Army were in cahoots with the West Germans in planning German Reunification!!!
The combined German military at this time was enormous. As big as the US Army and arguably better equipped and trained, and also totally concentrated in Germany.
http://forum.juhlin.com/showthread.php?t=3253
The Kremlin and the Red Army would have been shitting a brick at the prospect of fighting it.
In 1997 a cadre within the militaries of West and East Germany decides to reunify Germany by itself. They do not consult the civilian government of West Germany (or East Germany) or do they inform any of their NATO allies including the United States about what they are up to. This doesn't say much for trusting the Germans.
Also as Germany is occupying Poland what is to stop it from reclaiming the historical German territory in Poland that was taken from it at the Potsdam Conference in 1945. The whole issue of Potsdam was a very sore subject for decades among the West Germans, they infact did not recognise East Germany or would have any relations with any country who did until the 1970's. Basically Silesia will become a German state once again as will parts of Prussia. How long before they decide to reclaim East Prussia by taking the Kaliningrad Enclave and the Baltic States?
How will other European countries react to this? France, Belgium and Eastern Europe need I say more! Would Britain be happy with Germany posing a threat to the Low Countries and the English Channel? The Italians left NATO and joined the Warsaw Pact and then invaded Austria and Bavaria. I'd say they would be worried.
Germany of course has no nuclear weapons, but what would now stop it from developing them. The military is in control of Germany not the civilian government. Germany has an advanced nuclear industry capable of manufacturing reactors, enriching uranium, and fuel fabrication and reprocessing. It had 19 nuclear reactors at this time and was a leading exporter of nuclear technology. German companies are major participants in uranium enrichment that develop gas centrifuge technology and control domestically developed nozzle enrichment technology. Given the fact of its Cold War position on the front line in any potential war in Europe and the fact that nuclear weapons were likely to be used on German territory by the Soviets and perhaps NATO as well, it is highly likely that the Germans undertook design work on a range of nuclear weapon types themselves. Germany has the technological base to support a nuclear weapons program and members of the West German government were proponents of acquiring German nuclear weapons. It is known that Germany has considered manufacturing nuclear bombs for civil engineering purposes. In the early 1970s a feasiblity study was conducted for a project to build a canal from the Mediterranean Sea to the Qattara Depression in the Western Desert of Egypt using nuclear explosives. This project proposed to use 213 bombs, with yields of 1 to 1.5 megatons detonated at depths of 100 to 500 m, to build this canal for the purpose of producing hydroelectric power!! Mad stuff but it highlights how easy the Germans thought they could develop their own nuclear weapons.
So what we have here is 1939 all over again without the Nazis and with nuclear weapons. And were not even talking about China and the Middle East.