Complex sentence: On 23 May, Hitler described to his generals his overall plan of not only seizing the Polish Corridor but greatly expanding German territory eastward at the expense of Poland and he expected this time they would be met by force.
Split into simpler sentences: On 23 May he described to his generals his overall plan of not only seizing the Polish Corridor but greatly expanding German territory eastward at the expense of Poland. He expected this time they would be met by force.