The reason that they did this was because they truly didn't have much of a choice. Back then, soldiers had a different formation that we see now like in CoD or Battlefield. and even though they didn't know how many soldiers were down there, they didnt want to risk it. they also were not sure if it was worth it to charge the soldiers because of the fact that there wasn't much to salvage down in their camp if they won.
hope this helps :)
I am not sure what exactly you want to receive as an answer but Ill give 2 examples.
After the rise of the Third Reich Jewish people were forced to migrate from Germany to neighboring countries and a lot of them in fact fled to United States including the famous scientist Albert Einstein.
The other example is the forced migration of Native Americans during the settlement and colonization by the American Colonies as they were trying to go farther down the continent.
The answer is
C. The Islamic invasion
Answer:
A. It convinced many European Kingdoms to participate in the Crusades.
I believe it was because both blacks and whites were moving west to the cities to find jobs.
hope i helped :)