inductive reasoning about the causes of World War II
Induction is a reasoning when a general conclusion is gradually built on the basis of individual cases. This is the method used by Sherlock Holmes in Conan Doyle's detective stories, and not deduction, which is the exact opposite - when an explanation is brought from a general theory to individual facts. So, let's try to imagine that we know nothing about WWII, and only look at the facts separately...
There is Germany - once a great power that lost the war, which was significantly humiliated by the Versailles Agreements and disarmed, colonies were taken away, partially occupied (Ruhr, Saar).
There are allies - they defeated the Germans, have powerful armed forces, colonial possessions all over the planet. They overcome the crisis at the expense of reparations collected from Germany.
There is Poland - a new (or rather "new-old") country on the map of Europe, which in addition to purely Polish territories grabbed parts of German land in 1919-20 where Germans lived. Although Poland did not exist during WWI, it was allowed (with the permission of the Allies) to appropriate these territories. It is also - compared to Germany before 1933 - quite militarized.
At some point in Germany, the National Socialists come to power in elections. They rose on a wave of general German discontent with this situation. In 1934, the Germans concluded an agreement with Poland to secure their borders. Then there was quite successful cooperation, which reached its peak in the fall of 1938 during the Sudeten crisis.
And now, having restored almost all German territories, the National Socialists turn to the Poles. Although the situation was much worse for Germany than with the Sudetenland (Czechoslovakia in 1919, at least, did not seize territory from the bleeding country), Hitler tried to convey his position carefully, but was met with a decisive refusal from the Poles.
An attempt to soften the position by demanding the return of the corridor for the construction of an extraterritorial railway might have been successful, but in March 1939 Poland received guarantees from Great Britain. This gave the Poles a (false) sense of security, and discouraged any compromises with the Germans.
Then there was the tense summer of 1939, new attempts to reach an agreement, a customs war in Danzig, shootouts on the borders, the Gleiwitz incident and, finally, a full-scale invasion.
On the eve of the invasion, a non-aggression pact was also signed with Soviet Russia, since it became obvious that as a result of the war, Germany and its zone of interest would most likely border directly on the Soviet one.
On September 1, '39, there was no Second World War. It was only a German-Polish war over the Danzig Corridor. It did not start on the 2nd either. Only on September 3, when France and Great Britain declared war on Germany, did WWII become a legal fact.
So, from the particular facts presented above, let's move on to the general conclusion. After World War I, the Germans felt vulnerable compared to their neighboring powers. Germany was not solely to blame for WWI, which even official historians now admit, and yet it was cruelly punished. Discontent gave rise to opposition, and since 1933 the new authorities have sought to restore all the territories they had previously owned. By 1939, the process had actually come to an end, but the intransigence of the Polish government, together with the intransigence of the allies, ruled out a peaceful solution to the last territorial crisis.
In other words, Germany, although it bears the blame for starting the war against Poland (the German-Polish conflict over Danzig), is not the only one to blame for the outbreak of WWII. The latter became possible only as a result of the declaration of war on the Germans by the British and French.
This is the conclusion of inductive reasoning regarding the causes of the outbreak of World War II.