How were wars financed under Islamic empires?

Question

A related question is this thread, where the subject in question were banks, and how they operated and profited under Islamic rule.

In Islamic jurisprudence (fiqh), charging interest on loans is considered usury and is illegal. How did Islamic states fund their armies to wage war? Was it all plunder as you conquer or did the states take foreign loans and adhere to the interest?

I am looking for a broad range of how different Islamic empires operated their war finances, and maybe how it evolved over time. Basically everything from the inception of Islam to the collapse of the Ottoman Empire.

Answer 1

In the early Islamic empires, the state charged an alms tax on Muslim subjects (zakat). It was mainly intended for charity but war "in the path of God" (jihad) was also a permitted use for it. This tax covered practically all types of wealth, including not just gold and silver but also livestock, land rent, merchandise and agricultural produce.

There was also a poll tax charged on non-Muslim subjects (of which there are many), paid in gold or silver.

Finally, during the early conquests in places like Mesopotamia and Egypt, vast tracts of agricutural land was expropriated from the previous ruling class and claimed by the empire as an endowment for the Muslim community. The state charged a land tax on these called kharaj, which continued to be charged even though in practice the land was given over to a new Muslim land-owning class.

Of course, as with all other empires, plunder was both the object of conquest and helped finance further conquest. There were detailed rules under Islamic rule for how land and property could be taken in war and how it would be distributed between the state and the generals and soldiery.