The first function of power in Islam is deterrence. When you possess power and the capacity to project power, it can act as deterrence to your enemies. This is why the Indian government exploded its nuclear devices in order to demonstrate their capacity to project power. As a consequence it is used to intimidate.
Allah swt says, "Build your power, because if you possess power and the capacity to project that power, then the enemies will think twice before they ever cast an evil eye upon you." There is a corollary to this. The corollary is, "if you are weak, if you do not have power and the enemy perceives you not to have power, this will function as an invitation for hostile forces to attack you. The perception of weakness can invite aggression.
The second function of power in Islam is clearly spelled out in the Quran. In surahtul Hajj, chapter 8, Allah says that permission is now granted to you to wage war because you have become the victims of aggression. Others are waging war against you and so power is to be used to response to aggression.
Who are these people? Allah says, "If you do not build power you will not be able to respond to a people who is committing aggression and driving you out of your homes. You will not be able to respond when they are coming into your territory and they destroy the houses of Allah, where Allah’s name is mentioned frequently."
Allah is pleading, "This is My House. My House is being destroyed. Will you not build power to respond to that aggression?" Allah did not mention the masjid (mosque) alone. He mentions the synagogue, He mentions the temple, He mentions the church and then He mentions the masjid. Allah says, "My Name is mentioned frequently in these buildings."
Therefore building power is secondly for responding to aggression.
The third function of power – in surahtul An-Nisaa (The Women) chapter 4, Allah does not speak, does not make a statement - Allah swt is pleading, "What is wrong with you? Where has your manhood fled? Why don’t you stand up? Why don’t you fight in the way of Allah? For the liberation of them, man, woman and children, those who are weak, helpless, oppressed on the face of the earth" This is a revolutionary conception of an international order. This is a conception of an international order where you have the obligation to intervene in every single part of Allah’s earth in which there is oppression.
The fourth function of power – "If you don’t have power and the enemies of Allah can kick you around like a football, then mankind will not be persuaded when you have the truth."
The fifth and last function of power – in surahtul Al-Anfal, Allah says that when He establishes them on the face of the earth (take control of a territory), they establish His worship, and they collect the Zakat which He has ordained must be taken from those who have more and given to those who are in need. When He established you in the land with power, you will now use that power to establish an order in which justice will prevail, and in which values will be preserved, and you’ll use power to eradicate evils. In this you will see the demonstration that in the final analysis all things are with Allah.
The Philosophy of War in Islam
In Islam power is not to be used for aggression. The Quran and hadith are very clear on this: that you must first explore and exhaust all possible peaceful means of resolving a problem before you can resort to the use of force.
That Islam has a clear preference for peace over warfare. Indeed the heart of the Prophet Muhammad (saw) is a "peace loving heart". When Allah (swt) revealed to him, "Fighting is now made compulsory to you," Allah had to address him, to explain to him. "Listen, it may be that you dislike something, but in it there is benefit for you and it may be that you desire something, but in it there is harm for you. You do not like warfare but in it there is benefit for you. And if you prefer the non-violent way, there is danger and harm for you." "And Allah it is who has full and complete knowledge of what is good and what is bad for you. You do not have full and complete knowledge of all these things."
The Quran confirms that even while Allah has made fighting and the development of power obligatory, if at any time the enemy is inclined towards peace, and is also prepared to disgorge the fruits of aggression, then you must also incline towards peace.