1. The Battle Of Tours, 732
In the sixth century, the Muslim armies were a strong force, toppling great armies and claiming huge swaths of land. In the early sixth century, Berbers from Libya sailed into Spain claiming land for the Ummayad Dynasty. They took most of southern Spain, moving towards France. This was a serious attempt by the Muslims to take Western Europe and hadn't it been for Charles Martel, they would have likely succeeded.
Martel had led his armies to meet the Muslims. At first, they didn't get off to a good start and suffered several defeats. But when the Muslims got lazy, abandoning their posts, and started looting and pillaging local villages, Martel staged a last attempt and was able to turn the Muslims back to southern Spain. Had Martel's army been defeated, there would have been no other to stop the Muslims from entering Western Europe.
