The global government of Imam Mahdi (p. b. u. h)
The global government of Imam Mahdi (p.b.u.h)، From the comprehensive virtual encyclopedia of Wiki Mahdism
One of the most important achievements of Imam Mahdi's appearance is to form a global government, which means a transnational, trans-regional and trans-ethnic government. In this approach, the extent of Imam Mahdi's ruling moreover all Islamic tribes and clans, includes all other religions and nations of the world. Hence due to the widely related and authentic traditions narrated from the Prophet and the infallible Imams (p. b. u. t), the global government of Imam Mahdi (p. b. u. h) will encompass the East and West.
In Islamic thought, the achievements of this important issue have been pointed out from different angles and have been defined in two realms of "government" and "development of the government on a global scale".
The composition of Imam Mahdi's governance:
Formation a divine government
The government of Imam Mahdi (p. b. u. h) bears a divine structure and begins with the formation of an efficient administration. The usage of the verb "Yamliku" in the Islamic narrations indicates that he will govern all over the world, and as quoted from the fifth Imam of Shia, Imam Bāqir (p. b. u. h)), Imam Mahdi's government is among the last governments, and its strength is that no government can behave like it.  Paying attention to the content of the Hadiths, it becomes clear that the government of Imam Mahdi (p. b. u. h) is the best government that human beings have experienced, and there is no corruption in it. Also, Imam Mahdi (p. b. u. h) differs from the Imams before him on the matter of governance so that he is compared to Solomon the son of David, the prophet.  According to some narrations, Jesus helps the Imam to invite Christians from Rome [Europe] and China [Asia] to Islam. 
The benevolent government
In the doctrine of Mahdism, the title of "benevolent government" has been used to describe Imam Mahdi's ruling. This term can be seen in the texts of some supplications related to Imam Mahdi (p. b. u. h).  The governance of Imam Mahdi (p. b. u. h) is the actualization of divine promise in religions of the coming of the last savior. 
The officials of Imam Mahdi’s government
The agents of Imam Mahdi (p. b. u. h) have a special capability for doing their missions. They are mentioned in some Hadiths as the "owners of the flag" because they are obedient to the command of the Imam and the executors of his divine commands and to help him throughout the world. 
The style of Imam Mahdi's governance
According to Islamic narrations, the ruling of Imam Mahdi (p. b. u. h) has some specific features; for instance, he will judge in the manner of Prophet David.  In this type of ruling, the witness is not questioned; and this issue may refer to the high rank of the Imam's awareness and consciousness over all affairs, as stated in the narration. 
The achievement of Imam Mahdi's government
The most important achievement of Imam Mahdi's government is to establish a pervasive peacefulness on the Earth while supervising all affairs.  At that time, people in different parts of the world, declare their deep gratification of the Imam's agents.  In accordance with Islamic narrations quoted from the prophet Muhammad (p. b. u. h. and his household) the earth will be full of justice as it has filled with oppression and cruelty. In that era, the sky by a constant rain, irrigates the earth, and the earth grows a lot of plants and brings out its treasures. According to many authentic narrations, the Imam distributes the properties fairly, and he bestows wealth benevolently. At the time of his ruling, Islam becomes venerable. 
The time period of Imam Mahdi's governance
Through analyzing some Hadiths on the duration of his ruling, it becomes clear that there are different numbers of duration from five to three hundred and nine years.  Also resulting from the narrations received through the Companions of the Prophet (p. b. u. h) the Sunnis believe that the ruling of Imam Mahdi (p. b. u. h) would be inevitable. Abū Saˈīd al-Khudrī has quoted from the Prophet to have said that Imam Mahdi Imam would rule for five, seven or nine years. 
Two characteristics of Imam Mahdi's government
The global government:
As a Quranic divine promise, "Global government" is a prominent feature of Imam Mahdi's ruling. This is what God says in the Quran in different occasions; for instance, the Almighty Allah says in chapter al-Tawbah,
﴿هُوَ الَّذي أَرْسَلَ رَسُولَهُ بِالْهُدى وَ دينِ الْحَقِّ لِيُظْهِرَهُ عَلَى الدِّينِ كُلِّهِ وَ لَوْ كَرِهَ الْمُشْرِكُونَ﴾
“He it is Who sent His Messenger with guidance and the religion of truth, that He might cause it to prevail over all religions, though the polytheists may be averse. ”
Interpreting the above verse, it has been narrated from Imam al-Sādiq (the six Imam of Shia) to have said,
«عن أبي بصير قال: قال أبو عبد الله علیه السلام في قول الله عز و جل هُوَ الَّذِي أَرْسَلَ رَسُولَهُ بِالْهُدى وَ دِينِ الْحَقِّ لِيُظْهِرَهُ عَلَى الدِّينِ كُلِّهِ وَ لَوْ كَرِهَ الْمُشْرِكُونَ فَقَالَ وَ اللَّهِ مَا نَزَلَ تَأْوِيلُهَا بَعْدُ وَ لَا يَنْزِلُ تَأْوِيلُهَا حَتَّى يَخْرُجَ الْقَائِمُ علیه السلام.»
“Abū Basīr reports that he asked Imam al-Sādiq (the Shia’s sixth Imam) about the meaning of this verse and the Imam replied, “By Allah, the real meaning of this verse has not yet come to existence, but it will come to existence when al-Qā`im rises… . ’”
With the support of Imam Mahdi's governance, the enemies of Islam will be eliminated, and it will be possible for him to elevate real Islamic through his ruling in the East and West of the world. 
The obedience of other religions to Islam:
Another specific feature of the government of Imam Mahdi (p. b. u. h) is the obedience of the followers of other religions to Islam through accepting the universal Islamic government of Imam Mahdi (p. b. u. h). 
- Al-Ghaybah, by Sheikh al-Tūsi, p. 474.
- Ibid, p. 372.
- Ibid, p. 474.
- Al-Ghaybah, by Nu’mānī, p. 146.
- The Upriser.
- To govern.
- Our government.
- The benevolent government.
- Al-Kāfī, by Muhammad b. Ya'qūb al-Kulaynī, vol. 3, p. 424.
- Psalms of David, 37-9, 37-27.
- Kamāl al-Dīn, by Shaykh al-Sadūq, vol. 2, p. 673.
- Al-Kāfī, vol. 1, p. 397.
- Kamāl al-Dīn, vol. 2, p. 670.
- Kamāl al-Dīn, vol. 2, p. 673.
- The position of the teaching of Promised Savior from the viewpoint of Sunnis, by Mahdi Farmāniān, p. 185.
- "Research Mahdic" magazine, "A study on the narrations of the time period of Imam Mahdi's governance", by Mustafā Warmazyār, no. 6.
- Musnad, by Ahmad bin Hanbal, vol. 3, p. 27.
- The Quran, 9:33.
- Kamāl al-Dīn wa Tamām al-Ni‘mah, vol. 2, hadith 16.
- Ibid, vol. 1, p. 256.
- Bihār al-Anwār, vol. 51, p. 61.
- The Holy Quran.
- Ibn-e Ḥanbal Al-Shaybanī, Abū ˈAbdullah Ahmad b. Muhammad, Musnad, Beirut, Dar-e Sādir.
- Sadūq, Muhammad b. Ali, Kamāl al-Dīn wa Tamām al-Ni`mah, Tehran, Islamiyyah, 2016.
- Tūsī, Muhammad b. Hassan, Al-Ghaybah, Qom, Dār al-Ma'ārif 1990.
- Farmāniān, Mahdi, The position of the teaching of Promised Savior from the viewpoint of Sunnis, Mashreq-e Mowˈūd Magazine, no. 2, 2007.
- Kulaynī, Muhammad bin Ya'qūb, al-Kāfī, Tehran, Dar al-Kitāb al-Islamiyyah, 1986.
- Nuˈmānī, Muhammad b. Ibrāhīm, Al-Ghaybah, Tehran, Sadūq, 2018.
- Warmazyār, Mustafā, "A study on the narrations of the time period of Imam Mahdi's governance", "Research Mahdic" magazine, No. 6, 2013.