The correct order of the given events is as follows:
- Muhammad unified most of the Arabian Peninsula into a single Islamic state.
- Islamic forces conquered Mesopotamia by defeating the Byzantine people.
- The Umayyad army crossed the Strait of Gibraltar and conquered Spain.
- The Europeans attacked the Muslim Empire as part of the Crusades.
After the prophet Muhammad managed to set the ground for the new Islamic religion, he managed to unite the people on the Arabian Peninsula and created an Islamic state. This state was pretty powerful but also had as advantage that big portion of the countries around it and in Europe were not in the best of states, so the Islamic state was conquering new territories very quickly, including Mesopotamia, North Africa, and even got on European soil by conquering Spain. After the Europeans realized the danger they are facing and after the capturing of Jerusalem by the Muslims, they organized the Crusades and attacked the Islamic state.
