The physical feature that likely slowed the Muslim armies were the Pyrenees.
Explanation:
The Muslim armies were very strong, united, and quickly managed to use the bad situation in which the other kingdoms and empires were. The weakened armies, be it because of internal struggles or because of numerous previous wars, were relatively easy target for the Muslims. This led to rapid expansion of the Muslim caliphates, and with it rapid spreading of the Islam.
Once the Muslims managed to conquer Northern Africa, they turned their eyes toward Europe. Through the straight of Gibraltar, the Muslim armies easily entered the Iberian Peninsula, and easily managed to defeat the small kingdoms on the peninsula. Their expansion in Europe stopped there though, and one of the big factors that slowed them down, and helped the Europeans, were the Pyrenees, which proved to be an excellent natural protective barrier.
Other areas that were conquered by the Muslims were:
Learn more about Abu Bakr's influence on the spreading of Islam https://brainly.com/question/7134251
#learnwithBrainly