>>945
>France and Britain didn't suddenly declare war
There was nothing sudden about it. Britain guaranteed Polish independence in 31 March 1939. It was very clear that any invasion would be reciprocated, exactly as had been the case during the Sudetenland crisis, when war would have broken out a year earlier if Hitler had chosen to go ahead with Case Green.
>the dispute of post-weimar territory being handed out after failed negotiation of danzig
Just like the previous world war was about the rivalries between the great powers more than about Bosnia or the Archduke, what happened in September 1939 was not truly about Poland. You are onto something when you describe it as "two-sided" in that there was already a hostile international mood since the previous year. And in this context Hitler was not thinking exclusively within the scope of some forsaken Pomerelian land; his thoughts were on Paris and London, and his pressure on Poland was his way to escalate the tension. He was the one to fire the first shot, so to speak. It was his intention to have a war, and he had a rational basis for that.
Simply put, Germany's odds of a victorious war were not great at the moment but would decline with every passing year; if there was to be a war, then the best possible scenario would be an immediate war. The Reich was losing the arms race. It had already achieved a greater level of economic mobilization than any of the Western powers. It had mobilized so much that it was facing economic problems because of it: there was an expanding budget deficit, the money supply had doubled in two years, railways were in a poor condition, the quality of some consumer goods was in decline and so on. A Reichsbank memorandum submitted to Hitler's office on 7 January 1939 discusses this. Despite this, arms output had actually stagnated throughout 1939, as had previously happened in 1937, because of the crippling balance of payments limitation which Germany suffered since the late Weimar years. Not enough resources could be imported to sustain an acceleration of the rate of rearmament. The best that could be hoped for was to accumulate foreign exchange reserves for a while and go for one last burst of spending.
Meanwhile, the Western powers, despite mobilizing less of their economy, were rapidly expanding arms production and were set to win the arms race in a few years. They did not suffer from Germany's trade woes and had more developed economies in the first place. It's worth noting that interwar Germany had medium-level standards of living, less purchasing power per capita than France and Denmark and an incompletely modernized economy with a lagging, large agricultural sector; it was particularly far behind America, with its dramatic economies of scale, and since 1938 Roosevelt had been openly hostile, pushing for rearmament and trying to supply weapons to the French and British.
Those points were made by Ludwig Beck and Secretary of State Weiszaecker at the Sudetenland crisis and General Thomas in 1939. They were discussed in Berlin and Hitler was well informed of the state of the arms race. Hitler himself later explained this logic to Speer.
Nonetheless, the Reich had, at the moment, a slight superiority in the air and a dubious parity on land. Those were doomed to decline, but still existed at the moment. From a simple arms race perspective and the premise that a war would happen it would have been irrational for Hitler to
not provoke a war.
Besides the arms race, the diplomatic chessboard cannot be ignored. Since June 1938 Weiszaecker had correctly predicted that Germany would have to face France, Britain, the USA and the USSR. Yet for the moment the latter two would not attack. FDR was struggling with isolationists in Congress and Stalin had just become a near-ally. So, once again, the best possible starting point for a war was the present, when two of Germany's enemies could be counted to not immediately make a move.