Shortly after Muhammad died in 632 A.D., and shortly after Abu-Bakr became his successor, the central role of taxation in Islam emerged. Some Muslims who had followed Muhammad did not want Abu-Bakr as the next Islamic leader. According to World History: Patterns of Interaction, they
refused to pay taxes, and a few individuals even declared themselves prophets. For the sake of Islam, Abu-Bakr invoked jihad. The word jihad means "striving" and can refer to the inner struggle against evil. However, the word is also used in the Qur'an to mean an armed struggle against unbelievers. For the next two years, Abu-Bakr applied this meaning of jihad to encourage and justify the expansion of Islam.
Already in a very early stage of Islam's development, taxation is a major issue, and it is linked to jihad - linked to the military expansion of Islam. It is important to remember that the word jihad probably did once refer to an inner psychological or spiritual struggle against evil, and may even still occasionally be used that way. Note also that this first major Islamic tax controversy was not related to the taxation of the oppressed peoples in the lands conquered by Islam, but rather related to the taxation of Muslims by their leaders.
As Muslim armies conquered and occupied vast territories in Spain, North Africa, Arabia, Mesopotamia, and Persia, those subjected to Islamic military government would also face taxation. Those in such territories were taxed according to their religious status. If they converted to Islam, they would pay a lower tax rate. Those who chose to remain with their own culture's native religions were treated more harshly: "They paid a poll tax each year" which might be in coin, in agricultural goods, or in the form of having one's children confiscated to be slaves or laborers.
Starting around 750 A.D., the Caliphate - the Islamic empire - fell under the control of a dynasty called the Abbasids. One of their goals was to conquer and occupy Gaul - what we now know as France. The first attempted Islamic invasion of France was in 732 A.D., but this attempt had failed. The Abbasids would try again. This effort would require a large imperial military, and lots of money - money to be gained by taxation.
The Abbasids developed a strong bureaucracy to conduct the huge empire's affairs. A treasury kept track of the money flow. A special department managed the business of the army.
The Abbasids would fund their military buildup with taxes that disproportionately burdened the residents of lands occupied by Islamic armies, and of those residents, the taxes would disproportionately burden the non-Muslims, who conveniently lacked any political influence whatsoever. These non-Muslims were also, on average, poorer than the Muslims in their regions: poorer both than the locals who had converted to Islam, and than the occupying Islamic soldiers who were foreign to the region.
To support this bureaucracy, the Abbasids taxed the land, imports and exports, and non-Muslims' wealth.
But not all taxes collected were for military expansions. Some went to support the luxurious style of a the Caliphs - the leaders of the empire. Some went to support the mosques and the religious leaders - mullahs and imams. Some of it was collected for the purposes of helping the poor.
