I’m genuinely wondering why is wars important in Islam? Why did the deen spread by war? I don’t understand the spoils of war as well. It’s talked about in the Qur’an. I don’t want to say something which would make me deviate , so please don’t pass that judgment. I’m just not a war person and I don’t understand the idea behind taking things from the enemy when war is a traumatisizing experience.
War is what comes about when people cannot settle their disagreements peacefully. It is just a larger version of a fight between two people. Fighting is part of the lives of many animals, not just humans.
Humans fight because some people’s desires make them want to take things from other people or do things to other people. Humans have free will, meaning that even if they know everything there is to know about morality, they can still do evil things and harm others. The reason God rewards us for being good is that we have the power to be evil, it is for our choice to be good that God rewards us.
The Muslims peacefully suffered the oppression of the pagans in Mecca. The Prophet ﷺ did not ask his followers to start gathering weapons in order to fight back. As long as they lived under the rule of the pagans, they had to abide by their laws.
But when the Prophet was elected the ruler of the city-state of Medina, things changed. Medina was a sovereign state (it was not under the rule of any other country, it was independent) and had to defend itself against external threats. When ruling a country, you cannot say that you love peace and sit back and expect outsiders to be peaceful. If your country has something valuable, such as oil, then other countries will want to invade you and take the valuable things you have. As long as you are dealing with other humans, you need to have the power to defend yourself from them, because not all humans are good people who want peace. Many humans constantly desire more power and wealth and are willing to harm and kill others for it. There are thousands of rich factory owners who do not care that the chemicals they throw into the rivers can cause birth defects. They know what they are doing is wrong, but they do not care. What is needed therefore is a law (backed by men and women carrying weapons, i.e. the police) that prevents such people from polluting rivers.
The Prophet ﷺ had to deal with the threat from Mecca and other surrounding Arab tribes who wanted to extinguish Islam and kill him and his followers by creating an army. They ended up fighting the Meccans, then the Romans and the Persians started to threaten the Muslims, so the Muslims had to fight them, and in this way the war continued.
Eventually, the Muslim world was ruled by the Umayyads and Abbasids who were not always very religious. They acted like all other rulers act, wanting wealth and power and glory, so they encouraged people to wage wars in the name of Islam even though it wasn’t about religion, it was about power.
So asking why war was needed is similar to asking why the police is needed. It is needed because some people are not nice and are willing to kill you to take what you have.
As for the spoils of war, it is an ordinary part of war that the defeated army leaves behind its weapons and other things it has. The rules regarding the spoils are there so the Muslims do not fight among themselves over the spoils but deal with them in a civilized manner.