The Umayyad dynasty expanded the Islamic empire greatly after the death of Muhammad. Under the Umayyads, the Islamic empire grew to span parts of Africa, Asia, and Europe within 100 years. The Umayyad armies began with hit-and-run raids and soon launched organized campaigns of conquest, taking control of most of Central Asia by the 700s and North Africa and the Iberian Peninsula by 711. However, over time unrest grew under the Umayyads as they neglected Islamic law and treated some groups, such as non-Arabs, as second-class. This led to their overthrow by the Abbasids in 750.