What is the invasion of proland what happened and what caused it

The Nazis invaded Poland on 1 September 1939. The Nazis justified the invasion by suggesting that Poland had been planning to invade Germany, and with false reports that Poles were persecuting ethnic Germans. On the 17 September, the Soviet Union joined forces with Germany and invaded Poland.

Explanation:

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here are some events that to cause increased conflict between the north and south

1) mexican cession- gaining modern day california, utah, arizona, and new mexico from mexico. caused southern and northern politicians to fight over whether or not there would be slavery in these newly acquired territories.

2) uncle tom's cabin- this famous book described the cruelty of slavery in the south during the antebellum period, causing more northerners to support abolition and southerners to resent the book as they felt it unfairly depicted southern society.

3) kansas- nebraska act- disagreements over whether or not kansas and nebraska would be free or slave states caused issues between northern and southern politicians in congress.

4) bleeding kansas- this fighting took place in kansas after congress allowed this territory to vote on whether or not they would have slavery. citizens were killed and buildings were destroyed during this fighting.

c or d both can be the answer