The Mahdi is prophesied to have the same number of companions as Muhammad in the Battle of Badr – 313 – and the majority of them will be non-Arabs.
Imam al-Baqir (‘a) also said: “The supporters of Hadrat al-Qa’im (‘a) will be three hundred and thirteen persons who will be from the children of the a‘jam (non-Arabs). (An Overview of the Mahdi’s Government)
Growing up as a Shia, I witnessed disagreement among Shia scholars as to what this means. Some claimed that the 313 companions are the true followers of Muhammad and His household. Hence, the reason that the Mahdi has not yet returned is due to the shortage of true followers in the world. Since there are around 150-200 million Shias in the world, some have espoused a more pragmatic interpretation that there are 313 commanders in the Mahdi’s army.
In the battle of Fort Tabarsi, the Báb’s army comprised of 313 combatants and they were Persians, that is to say, non-Arabs.
The catastrophe of Shaykh Tabarsi, which robbed Him of His ablest lieutenants, Quddús and Mullá Ḥusayn, and which engulfed no less than three hundred and thirteen of His staunch companions, came as the cruelest blow that had yet fallen upon Him, and enveloped with a shroud of darkness the closing days of His fast-ebbing life. (The Dawn-Breakers, p. 653)