An estimated 50,000 to 60,000 migrants entered the Spanish North African territory of Ceuta from Morocco in a two-day period. This is one of the largest mass border crossings in recent years. However, according to Spanish authorities, more than 48,300 migrants had returned to Morocco by Friday. Many of them said they returned due to lack of food, water, and shelter. At least 60 people died during the border crossing.This incident has also sparked political debate across Europe on immigration and border security. Why did so many migrants suddenly enter? Who are they? And why did they suddenly return to...