In the city of Samarra, at the time of Imam Al-Hadi (peace be upon him) a significant number of Shia noble men came together and Imam managed to direct them and deliver the message of Imamate across the world of Islam through their help by writing letters, etc. These noblemen expanded these Shia networks in Qom, Khorasan, Ray, Medina, Yemen and some remote regions and all around the world then day by day, the number of individuals who believed in this school [of thought] grew larger. Imam Hadi did all these great works under the sharp and blood-shedding swords of the six caliphs and despite their will. The Caliphate did not know them, because if it did, it would slay them all; however since these men had created a strong network, the caliphate could not reach them.

One day of endeavor by these honorable figures [The Infallibles, peace be upon Them] had its influences over the years; these honorable men safeguarded religion with such efforts, otherwise our religion should have not survived at all while having Motowakkel, Mo’tez, Mo’tasem and Ma’moun as its heads or Yahya Ibn Aktham- who was a number one in open and public corruption and vice- and alike as its scholars; This religion should have been eradicated from its roots on the same days and it should have terminated forever. It was the endeavors and efforts of the Imams (peace be upon them) that saved the Quran, Islam and religious teachings; this is the quality of God’s pure and sincere servants and His saints.

Certainly on the path of fulfilling such great tasks, one may get beaten, imprisoned or martyred- which are all insignificant for these honorable figures.

During these 250 years of Imamate- the 250 years since the decease of the Prophet of Islam (peace be upon him and his family) until the demise of Imam Hassan Al-Askari- our Imams suffered a lot, were martyred and were oppressed and it is fit to cry for them; as their innocence and oppression attracts hearts and feelings; but these oppressed men gained victory- both in a particular historical time and in general throughout all the times. 
Ayatollah Khamenei, 22/05/2012