Imam al-Mahdi (a.s) was born on the 15th Sha'ban 255 A.H. in Samarra, Iraq. He became the Imam when his father was Martyred in 260 A.H. Imam al-Mahdi (a.s) was only 5 years old when he went into ‘ghaibat' (concealment). The Imam's ghaibat was divided into two periods: Ghaibat-us-Sughra and Ghaibat-ul-Kubra.
Ghaibat-us-Sughra
Ghaibat-us-Sughra means ‘the minor concealment.' Its period was about 70 years. It began in 260 A.H. when Imam al-Mahdi (a.s) first went into concealment, and ended in 328 A.H.
During Ghaibut-us-Sughra, the Imam appointed some agents to represent him and the people. The Imam had four agents. After the death of the fourth agent, the Imam went into major concealment (Ghaibut-ul-Kubra). This was on the 10th Shawal 329 A.H.
The Signs Heralding the Reappearance of Imam al-Mahdi (a.s)
Prophet Muhammed (s.a.w.) has said: "Even if the entire duration of the world's existence has already been exhausted and only one day is left before Doomsday, Allah will expand that day to such length of time as to accommodate the kingdom of a person from my Ahlul-Bayt who will be called by name. He will fill out the earth with and justice as it will have been full of injustice and tyranny (by then)"
From this Hadith, it is clear to every Muslim that the twelfth Imam will reappear when this world is full of sins and injustice.
There are many signs mentioned by the Masumeen (a.s) on the reappearance of the 12th Imam. It is reported in Biharul Anwar that after the last pilgrimage the Prophet made, the Holy Prophet (s.a.w.) stood near the Kaaba, and called his people to listen to him. The Prophet said: "listen to me carefully so that you transmit these words of mine to those who are absent today." The Prophet began, "My people, a time will come when kings and rulers will be tyrannical." The Prophet also said that the payment of Zakat will be stopped.
According to the Masumeen (a.s), Muslim countries will seek aid from non Muslim countries. This is already evident in a number of Muslim countries. Another prediction that is come true is that 60 impostors will claim to be Prophets. By their attractiveness, their persuasion, and their personality, they will misguide the people. 58 false Prophets have already emerged since the days of the Prophet (s.a.w.). We have only two more to witness.
It is reported in Qayamat-e-Sughra citing "Oqdatud-Durr" that Hazrat Amir (A.S) has said that the Mahdi will not appear until one-third of the world population will die by being killed and one-third will die as a result of epidemics.
The Last Signs Heralding the Appearance of Imam al-Mahdi (a.s)
There is a Hadith from Imam Muhammed Baqir (a.s) that for three or seven consecutive days, one will see reddish yellow fire raging in the East.
Sufiani will emerge in Palestine, where he will start a revolt in the month of Rajab. He will be an uncompassionate rebel and his rule will last for eight consecutive months. He will conquer and rule Egypt for four consecutive months. Sufiani will conquer Tunisia, Algeria, Morocco, Jordan, and Syria. Sufiani has been specifically described by Aimma A.S. as an ugly, blistered, green-eyed, cross-eyed person who will be an enemy of the friends of the Ahlul-Bait. Imam Ali (a.s) has said that Sufiani's hatred of the devotees of the Ahlul-Bait will be such that any person named Ali, Fatema, Hassan, Hussein, Zainab, Ruquaiya will be arrested and beheaded straight away without further investigations. Sufiani will rip the Mimber of the Holy Prophet (s.a.w.). The holy house of the Prophet which contains his grave will be pulled and used as a stable. Horses will be tied in that Holy place.
Sufiani will then decide to attack Makka. His purpose would be to demolish the Holy Kaaba and kill the entire population of Makka. Sufiani's army will set out via Baghdad but, as Allah would have it, when they get between Medina and Makka, in the desert of Baida, suddenly one night they will hear a voice from the sky which will say, "O Baida eat up the entire army of Sufiani." It is said that the entire army numbering 100,000 persons will be swallowed up by the earth, except for two. The two who will be spared will suddenly encounter an angel. He will slap both of them turning their faces right round, looking behind instead of front. And that will be the time when Imam al-Mahdi (a.s) will already have reappeared in Makka. The Imam will establish his authority in the Holy Mosque at Makka in the Haram. The angel will then order one of them calling him Bashir. "O Bashir, go straight to Makka, into the Haram and inform the Imam that Sufiani's army has been swallowed up by the land. The other called Nazir will be ordered to go to Sufiani and tell him that the Imam has already appeared. He should proceed straight to Makka and declare allegiance to him.
Sufiani will prepare to attack the Imam but will not have enough courage. The Imam will catch Sufiani in Jerusalem and will kill him.
Imam Ali (a.s) has said that nine definite signs will precede the emergence of Hazrat Mahdi (a.s). These nine signs are:
Dajaal will emerge. A loud voice will be heard from the sky. Sufiani will appear and wage a fierce war. The army of Sufiani will be swallowed by a sudden opening of the land between Makka and Medina in the desert of Baida. A revered wise saint will be murdered in Makka. (This saint is to be a Hashimite descent.) A Seyyid descendant of Imam Hassan (a.s) will emerge with his army. The army of Seyyid-e-Hassan and an image of a man will appear in the sky opposite the sun. There will be two eclipses in the holy month of Ramadhan contrary to the normal order and calculation and the eclipse of the moon. On three occasions a loud voice from the sky will be heard in the holy month of Ramadhan.
The Reappearance
Hazrat Isa, Hazrat Khizr, Hazrat Ilias, and Hazrat Idris (a.s) will give allegiance to the Imam when he reapers. Also Jibrael will announce 313 companions of the Imam. These 313 companions will be people of eminent piety, great knowledge and absolutely steadfast in their determination and faith towards the Imam. Another 1000 people will be in the army of the Imam. These people will fight battles and kill enemies like Dajal, who will appear from India. Dajal will have the musical tunes with him. Then the Imam will lead the prayers, Hazrat Isa (a.s) will be behind him.
Lets all pray for the reappearance of Imam al-Mahdi (a.s).
source : www.sibtayn.com