Key events in the career of former Iranian President Mahmoud Ahmadinejad, a hard-line firebrand who has surprised Iran by filing paperwork to seek the presidency again in next month's election:
Oct. 28, 1956: Ahmadinejad born in the city of Aradan in Iran's Semnan province.
2003: Ahmadinejad becomes mayor of Tehran, Iran's capital and largest city.
2005: Ahmadinejad becomes Iran's president, issues a series of provocative statements against the U.S. and Israel.
2006-2010: The U.S. succeeds in getting four rounds of U.N. sanctions passed against Iran. They demand Tehran stop enriching uranium and exporting weapons, and they set banking, trade and travel restrictions.
2009: Obama takes office promising engagement with Iran. Months later, Ahmadinejad gets another term as president after a contested vote and a violent, postelection crackdown. The U.S. and Israel covertly sabotage Iran's nuclear program.
2011: U.S. and Iran support opposing sides in Syria's civil war. Tehran actively helps Syrian President Bashar Assad, while Washington slowly expands aid to the rebels.
2012: U.S. begins working with countries around the world to reduce oil purchases from Iran. A year later, Iran's exports drop by half, leaving its economy in tatters.
2012-2013: Several rounds of nuclear negotiations between Iran and world powers fail to make progress.
2013: Hassan Rouhani assumes the Iranian presidency, promising a new course of moderation.
2015: Iran reaches landmark nuclear agreement with world powers in which it curbs uranium enrichment in exchange for sanctions relief. The agreement goes into effect the following year.
September 2016: Amid suggestions Ahmadinejad may run again for the presidency, Iran's Supreme Leader Ayatollah Ali Khamenei recommends an unnamed candidate not seek office as it would bring about a "polarized situation" that would be "harmful for the county." Ahmadinejad announces he won't seek the presidency.
March 5, 2017: Ahmadinejad launches his own Twitter account, writing in English for his first post: "In the name of God Peace be upon all the freedom loving people of the world (hashtag)Imontwitter." He also begins posting candidate-style videos.
April 12, 2017: Ahmadinejad files to run for president again, shocking Iranians.