The reasons for war
Just a few days later, Europe was at war again. What explains it? For that the scenario facing Germany’s leadership should be understood.
First, it’s important to establish that they, including Hitler, were well-informed of the geopolitical chessboard, the state of the arms race and the economic and military strengths of the great powers.
Hitler derided whoever tried to sway him to a less hawkish path and banned subordinates from trying to convince him with pessimistic statistics, but he was no fool and miscalculation or lack of information are not what explain his actions in this moment.
Though he didn’t delve into technical details, he knew the strength of his enemies and kept himself in track of how many armaments Germany could realistically produce. He had the final say in the steel quota reductions that crippled rearmament in 1937 and 39. He adjusted his time horizon according to these realistic capabilities and played with international tension to put pressure on the arms race.

The following situation was presented to him in August 1939: the USA and USSR, though long-term enemies, were, for a time window, off the board on any war with France and Britain.
If such a war were started immediately, at least limited offensive victories could be achieved, though the final outcome was very dubious. If it began in 1940, the speed of the powers’ armament economies meant Germany’s relative strength and overall chances would decrease. In 1941 even more and so on. Time was an enemy.
This meant that, if a war was to begin, Germany had the highest chance of victory if it began immediately. Any further wait would increase its chance of defeat. Thus, based on the conditions of diplomacy and the arms race there was a case for starting a war immediately. Hitler himself would later explain this to Albert Speer.

But this alone is not enough of an explanation. Though Germany’s best shot at a war would be an immediate war, it would still be an extremely risky shot. It only had parity, not superiority in strength. Unless it could achieve immediate victory, and that was unlikely, its enemies would still be able to bring their economic superiority to bear. Even such a war was likely to end in defeat, and it did. So why did Hitler commit to such a tremendous gambit? Ideology must be taken into account.
Britain was hostile despite Hitler’s geopolitical calculation that his continental aims would not threaten it, and likewise, friendly to America despite his belief that they were inherently antagonistic. For him, this contradiction was explained by the actions of world Jewry. Those, too, extended to all the “flanking powers” –France, Britain, America and Russia- and this ties in to his understanding of history as a battle for survival between peoples.
The coalition facing him was a sinister one and the war that could happen would be a struggle of annihilation over which Germany would perish or secure its existence. Waiting would not help as the present peacetime position was precarious enough. A victorious war was the only guarantee of survival.