World War II: Why Poland Was Invaded?

Could you tell me why Poland was invaded?

A: We were invaded because of the land given to us at the treaty of Versailles. Hitler told Britain and France that the invasion was just a defensive action but that was a lie. The real reason was that he wanted Germany to have more living area for his people that he claimed were superior than everyone else.
Hitler was originally planned to attack us on August 26 but that changed because he found out that Britain had signed a treaty with us saying if we were invaded they would send troops to help us. Hitler used propaganda and misinformation to delay Britain from intervening with their attack. Our president feared for an attack but Britain and France persuaded him not to call in troops until August

I disagreed with this plan and thought we should have listened to the French and deployed the soldiers behind our two rivers which would act as a natural barriers. The French and British estimated that Poland would be able to hold out on it’s own for 2-3 months. After that they would begin to rely on the troops sent in by France and Britain. Britain and FRance had expected the battle to turn into trench warfare but no one notified Poland about this and we kept our same attack strategy. Our defensive strategy had our soldiers stretched thin and we were on disadvantageous terrain. Our supply lines were poorly protected due to our defensive strategy.

How did everyone in Poland handle the invasion?

The soldiers were prepared but the the civilian population was unprepared. The Polish propaganda before the war told everyone that in case of an attack Poland would easily be able to repel any attack from the Germans. When the civilians heard of our losses on the front line they were shocked. Since the civilians were unprepared they retreated to the east spreading chaos. This lowered troop morale and made transportation for the Polish troops very difficult.

What were the casualties of the