When facing a question like this, you may find a group of people who try to justify that Islam is not a religion of peace. They usually refer to terrorist attacks by pseudo-Muslims and conclude that Islam is not a peaceful religion. Peace in Islam is a value and an ultimate goal of life; may it be personal, social or worldwide.

But let’s see what is Islam’s viewpoint about war and if it approves terrorism.

What Do We Mean by Peace in Islam?

Before discussing the main topic of this article, we have to understand what peace in Islam means. According to Merriam Webster dictionary, “peace is a state of tranquility or quiet such as:

Freedom from Civil Disturbance
A state of security or order within a community provided for by law or custom.
Freedom from disquieting or oppressive thoughts or emotions 
Harmony in personal relations.” [1]

Therefore, there are two types of peace defined above; social and individual. Islam not only talks about individual peace, but also all of its rules are based on logic to shape a peaceful society. In this article, we would focus on social aspects of peace in Islam, either within one country or on what goes on between different countries.

Peace in Islam

Allah emphasizes in the Quran that Prophet Muhammad (PBUH&HP) is a mercy towards all human beings: “We did not send you but as a mercy to all the nations” (21: 107). It can be understood from this verse that a worldwide mercy, peace, and tranquility is the goal of sending Prophet Muhammad (PBUH) with the religion of Islam.

Imam Ali (AS) in his letter to Malik al-Ashtar (his appointed commander in another country) wrote: “Develop in your heart the feeling of love for your people and let it be the source of kindliness and blessing to them. Do not behave with them like a barbarian, and do not appropriate to yourself that which belongs to them. Remember that the citizens of the state are of two categories. They are either your brethren in religion or your brethren in kind. They are subject to infirmities and liable to commit mistakes.”  [2]

He specifically notes that we should be tolerant of people who have no bad deeds against Muslims and the religion of Islam.

Are Muslims Peaceful towards Everyone?

In social relations The Quran defines Muslims as moderate people; “Muhammad, the Apostle of Allah, and those who are with him are hard against the faithless and merciful amongst themselves. “ (48:29)

By referring to the above verse and by going through its interpretations we find out that “Muslims should be harsh on infidels. Who are these infidels? Muslims should not be harsh on anyone who does not believe in Islam. They should behave kindly towards those who are not opposed to them, who do not plot against them, and who do not seek to wipe out their nations - even if they follow other faiths.” While at the same time “Muslims should be harsh on those who fight against Islam and their identity, nationality, country, independence, honor, dignity, traditions, culture, and values.” [3] Therefore, it is completely rational for Muslims to defend themselves while their values are being attacked, and it has no contradiction with their peaceful nature.

Does Islam Allow Terrorist Attacks?

In recent years we have seen different terrorist groups such as Taliban, Al-Qaida or ISIS, who under the name of Islam, have committed terrorist attacks in different countries. They refer to verses of the Quran that are about the holy struggle (Jihad) and use those verses as a permission for their terrorist acts.

However, their interpretations of the verses of the holy struggle (Jihad) are not correct. The fact is that war is prohibited in Islam, and Muslims are not allowed to start a war against other countries for the sake of conquest or even for spreading the religion of Islam. Jihad is allowed for Muslims only if:

They are attacked by other countries, and their lives and properties are at risk.
If other Muslim territories are under attack by oppressive governments.
If other powers attack Muslim territories to annihilate Muslims or their religion.

“In the holy struggle (Jihad), violating or infringing on others' rights is not allowed. Killing other people under baseless pretexts is not part of the holy struggle (jihad). Neither is killing those who are not Muslims. Such acts are not allowed in the holy struggle (Jihad). Not all those who believe in religions other than Islam should be treated with harshness. Rather, only those who are opposed to Islam, your independence and territorial integrity, and Islamic culture, identity, and values should be treated with harshness. If carried out under these conditions, the holy struggle (Jihad) is considered as a divine order and will bring about glory to nations.” [4]

It is only under these conditions that Muslims are allowed to fight against the oppressors. And even when they are allowed to defend themselves and enter the war, they have to make sure to follow the rules of war. They are not allowed to kill the children or elderly of the infidels, or to poison the cities of the infidels. [5]

They have to tolerate the refugees, and if they betray them, they will face punishment [6]. Also, they should observe the rights of the captives of war [7]:

“Allah does not forbid you from dealing with kindness and justice with those [polytheists] who did not make war against you on account of religion and did not expel you from your homes. Indeed Allah loves the just. Allah forbids you only regarding those who made war against you on account of religion and expelled you from your homes and supported [the polytheists of Makkah] in your expulsion, that you make friends with them, and whoever makes friends with them—it is they who are the wrongdoers.” (60: 8-9)

Islam Is a Peaceful Religion, not a Passive One

In conclusion, Islam is a religion of peace for Muslim people and peaceful people. It is not a passive religion to sit and watch all the cruel things that are happening in the world and smile at it. Islam is the life map for those who wish to reach human perfection which is only achieved by obeying all of its rulings. No matter you call it Islam or something else, but every sane human being, by studying The Quran and searching about Islam, will understand that Islamic rules have been designed to make the society a safe place for human growth.

References:

1. peace
2. Malik Ashtar richest treasure
3. view of Jihad
4. ibid
5. Mafatih al-hayat, p. 318
6. Mafatih al-hayat, pp. 419- 20
7. Mafatih al-hayat, p. 423

Mahdi (as) is a messianic figure in Islamic eschatology who is believed to appear at the end of times to rid the world of evil and injustice. He is said to be a descendant of Prophet Muhammad (PBUH& HP) who will appear while Jesus Christ (Prophet Isa-ibni Maryam) accompanying him and will lead the believers to rule the world and fill it with justice and peace. This is what the Quran says:

 And We wanted to confer favour upon those who were oppressed in the land and make them leaders and make them inheritors. (Al-Qasas 28:5)

Who is Mahdi (as)? 

The name Mahdi is derived from the Arabic root h-d-y, commonly used to mean "divine guidance". Though Imam Mahdi features in both Shia and Sunni understandings of Islam, they differ in his attributes and status. Among Twelver Shi’as, Mahdi is believed to be the son of the eleventh Imam, Imam Hasan al-Askari (d. 874), and is said to have been on divine occultation (ghaybat) by God’s will. However, the Sunnis assert that he (Imam Mahdi) is a descendant of Lady Fatimah (SA), the daughter of the Prophet Muhammad, and it is unknown whether he was born or not.

What is the View of Muslims About Mahdi (as)?

According to our belief, one of the most extraordinary acts of worship is to wait for the promised saviour, and this waiting means trying to provide the conditions for his reappearance.

In the Shi'a Islam, or the school of Ahlul-Bayt, the eschatological Mahdi was commonly given the epithet al-Qa'im, which can be translated as “he who will rise”, signifying his rise against tyranny in the end of all times. Distinctively Shi'a is the notion of the temporary occultation of Imam Mahdi, whose life has been prolonged by God’s will.

As in above mentioned, the Sunnis also believe in the promised Mahdi and many hadiths about him have been narrated in their books. Abu Dawood quotes Prophet Muhammad (PBUH & HP) as saying: " Mahdi will be from my household, from the descendants of Fatimah”. And another hadith states: “Even if only one day remains [until the doomsday], God will lengthen this day until He calls forth a man from me, or from the family of my house, his name matching mine and his father's name matching that of my father. He will fill the Earth with equity and justice just as it had previously been filled with injustice and oppression”. (Furnish, 2005, p. 14) According to narrations before the arrival of Imam Mahdi, the earth would be filled with chaos. While divisions and civil wars, moral degradation, and worldliness would be prevalent among people, injustice and oppression would be rampant throughout the world. The Dajjal (The Anti-Christ) would appear and will spread decadence and corruption in the world. With an army bearing black banners, which would come to his aid from the east, Imam Mahdi would confront the Dajjal. Jesus would pray behind Imam Mahdi and then will kill the Dajjal. The Sufyani, another representative of the forces of the dark, also features in the traditions. He will rise in Syria before the appearance of Imam Mahdi. When the latter appears, the Sufyani, along with his army, will either be swallowed up en-route to Mecca by the earth by God's command or defeated by Imam Mahdi.

What Role does he have in the Future of Humanity

In Imamiyyah (Twelver Shiism), the largest Shi’a branch, believing in the messianic imam is not merely a part of the creed, but is the pivot. For the Twelver Shi'a, Imam Mahdi was born but disappeared after a while, and he would remain hidden from humanity until he reappears to bring justice to the world at the end of time, a doctrine known as the Occultation. This Imam on occultation is the twelfth imam, named Muhammad, son of the eleventh Imam, Hasan al-Askari. According to the Twelvers, the Mahdi was born in Sammara around 868, though his birth was kept hidden from the public. He lived under his father's care until 874 when the latter was killed by the Abbasids. 

Shi'a scholars have argued that the prolonged lifespan of Imam Mahdi Mahdi is not at all unreasonable given the longevity of  the Prophet Noah, Khidr and Jesus, as well as secular reports about long-lived people. According to scholars Imam Mahdi is viewed as the restorer of true Islam, and the restorer of other monotheistic religions after their distortion and abandonment. He establishes the kingdom of God on earth and Islamizes the whole world. As a matter of fact, in their true form, it is believed, all monotheistic religions are essentially identical to Islam as "submission to God." It is in this sense, that one should understand the allegation that al-Mahdi will impose Islam on everyone. His rule will be paradise on earth, which will last for several years until his decease.[1]

References:

1. (Sachedina, 1981, p. 176-178)