From the outbreak of the war to the signing of the contract, it took just over two months.
If we only consider the duration of Germany's combat operations against Poland, it was even less—just one and a half months.
The fact that a nation with millions in its military could be eradicated in one and a half months was unimaginable for all countries.
Keep in mind that no major wars had erupted after World War I, and the primary combat strategies of nations had remained entrenched in those of the World War I era.
Poland, for example, deployed massive infantry to dig trenches and engage in defensive combat, while positioning a large cavalry on the flanks, ready at any moment to encircle and attack—the prevalent tactical thinking of nations.
But the Germans changed this status quo, showing new ways of warfare to the entire world, including Britain and France.