Why Hitler risked war before German preparations were complete

Why did Hitler attack Poland before the later date around which German preparations had been discussed?

One explanation is that earlier unopposed gains encouraged him to believe Britain and France would again avoid war.

Germany's incomplete preparations make the early attack on Poland a question about political expectations as well as equipment. Hitler had previously encountered little resistance to territorial gains. One explanation offered is that he treated the lack of war over Czechoslovakia as evidence that Britain and France would also avoid war over Poland. In that interpretation, he expected another successful gamble rather than the wider war that followed. Large territorial gains did not remove Germany's logistical weaknesses, including continued dependence on horses and marching troops. The distinction matters because a force capable of a rapid campaign may still be poorly prepared for the longer war its attack starts.