Japan started the war by attacking Pearl Harbor. German had a pact with Japan. That was why Hitler declared war on the U.S.
I can't agree with #20 that the turning point was when Britain held out against the German Blitz. Hitler turned on the U.S.S.R. and came close to beating them. Neither Britain nor the U.S. could offer the U.S.S.R. much in aid because of the huge geographical problems. Germany held Norway and had land-based bombers all along that coastline to attack convoys. If Germany had beaten the U.S.S.R. they could have dominated the entire land mass of Europe, Asia, the Middle East and much of Africa. Then there would have been a long period of consolidation outlasting Hitler's lifetime. Germany would have doubled or tripled its territory and its population. France would have remained a satellite. The British Empire and the British navy would have withered on the vine--which is what they have done anyway, in spite of being on the winning side. The U.S. would have had to accept Germany as a major world power, just as it is presently accepting China and Russia. It all hinged on Germany conquering the U.S.S.R. I think Napoleon was faced with the same problem when he decided he couldn't invade Britain.
We must consider the impact of the emphasis on the Holocaust on Germany's ability to make and sustain war. While Hitler was interested in world domination, his priority was ensuring that the "parasites within Germany" were eliminated first... otherwise (in his mind), he could never have built a strong Germany. Hitler's obsession compelled him to order trains carrying Holocaust victims to have priority passage even before trains carrying troops. He had his best scientists working on experiments on Holocaust victims, not on the technology. Some of the best scientific minds in Germany before the war emigrated to escape the Holocaust.
I would like to believe that nothing in human history was "inevitable"; however, the odds were certainly stacked against Germany. Many historians seem to wonder if different decisions had been made (to not invade the Soviet Union, or to invade Britain with ground forces following Dunkirk) that things may have been different. But, I would submit that geography alone may have eventually defeated Germany anyway... being situated in the middle of Europe has always been a militaristic thorn in Germany's side... I believe that regardless of outcome, they would ultimately have been spread too thin over Europe and would have crumbled... same as the Mongols, same as the Romans, too much territory with not enough force.
Hitler's initial plan for Lebensraum which he layed out in the early '20's stated that he would continue German re-militarization until at least the late 40's, if not into the '50's. Had he followed his plan and not deviated due to his own mental instability, I believe that there is no question that Germany might have been successful, especially if he had ensured American ostensible neutrality. The German industrial infrastructure was capable of a sustained regional, or European war. However, British technological advances which only emerged late in the Battle of Britain would certainly have mitigated Hitler's significant advantage in the air. The British navy, that historic bulwark of protection from invasion, continued to maintain dominance of the seas, in spite of German U-Boat hegemony. Essentially, had German war aims been directed by a more lucid leader, there is much to support a German victory in the war.
Some commentators think that Hitler could have stopped and consolidated his holdings after defeating France. But what would he have gained economically? He wanted territorial expansion and access to more natural resources, among other things. Furthermore, he would have been left with two potential enemies, Britain and the U.S.S.R., who would both be able to build up their armaments and train their men. In just one year the U.S.S.R. would have been much better able to sustain a German invasion, and the British would have been able to build thousands of Spitfires and train the pilots to fly them. Hitler's big advantage had been that he had attacked nations that were inadequately prepared to defend themselves. Even the U.S.A. was heavily involved in rearming for "defense" and probably would have been brought into the European conflict sooner or later. It would be like a repeat of World War I. Hitler had plenty of problems.
There are people who maintain that everything that has ever happened since the Big Bang occurred some thirteen and a half billion years ago has been inevitable, since every effect must have a preceding cause and all the causes and effects could conceivably be traceable back to the Big Bang. Therefore, looking backward it would be impossible for Germany to win the war. Their defeat was predetermined in the Big Bang, as was every incident in the war and every incident in their entire history. From this point of view everything that will ever happen in the world down to the smallest detail is already predetermined--as is everything that will happen to us for the rest of our lives. Looking backward, it was inevitable that Britain would refuse to surrender, that Hitler would invade the USSR, that the Soviets would use geography and weather against his forces, that the Americans would get involved, and that everything would unroll exactly as it did, right up to the point where Hitler stuck a gun in his mouth and pulled the trigger. Is this possible?
I do not think that Germany had a sustainable plan, especially on the Eastern Front. Toward the end of the war, Germany was running out of soldiers and the Allies were gaining ground. Morale was down both amongst the civilians and the army. People were losing faith in Hitler as be became to seem more deranged and they were beginning to feel the effects of constant war.
Of course, hindsight is 20/20, and there is, practically speaking, no way of being certain that all the other actions would have had the same results if only one condition was changed.
However, it seems to me that Germany had no chance of winning. Hitler had seriously overextended his ability to support and resupply his troops, the Allies had much greater resources to replace people and equipment, and the mental and emotional commitment and support of the public was much stronger on the Allied home fronts than in the Axis countries. While this last may not have been as immediate and direct a factor as the earlier ones mentioned, I think it was a significant part of the resolution to continue the fight as long as needed.
I think his defeat was inevitable once he decided to attack the USSR and expose himself to a war on two fronts. I personally think the Axis powers could have maintained power throughout their holdings in continental Europe before Operation Barbarossa. It is unlikely the Soviet Union would have launched an offensive, and with the Germans focusing all their defenses to the west the US and Great Britain would have had a much more difficult time liberating western Europe.
Evidently, Adolph Hitler did not read thoroughly the history of Napoleon Bonaparte. Russian winters always defeat the enemy and meglomania is self-defeating.
I don't think Hitler's "irrationality" was to blame for Germany's defeat. Hitler bucked his generals time and again before the war and early in it. At that time, his plans worked and he was a genius. Later on, they didn't and he was "irrational." I think that Germany really was doomed because of the huge material advantages enjoyed by the Allies, particularly given that they had their unsinkable supply and operations base (Britain) so near the French coast.
I would say yes, their eventual defeat was inevitable because, by most accounts, Hitler had become irrational. He was no longer making decisions that worked militarily for Germany. Perhaps, if he had been deposed and somebody else had taken over, Germany might have been more successful.
Like the question about Japan, there are no such things as inevitabilities. Many things could have happened to change the course of the war in Europe. Germany not only came close to defeating the USSR, they also came close to surrounding and completely destroying the British force in France. They also nearly broke the back of the Allied advance in the Battle of the Bulge. So while I agree that fighting a two-front war against the combined might of the Allies placed Germany at an extreme disadvantage, victory was likely, but not inevitable.