Iran celebrates the 40th anniversary of the Islamic Revolution's victory on Monday at a time of heightened tensions with the United States and a sharp economic downturn.
On February 11, the state has organised a march to Tehran's Azadi (freedom) Square to mark the day the monarchy was officially toppled 10 days after the triumphant return from exile of the revolution's leader, Ayatollah Ruhollah Khomeini.
It will be a who's who of Iranian politicians and public figures, with President Hassan Rouhani expected to deliver a speech at a rally.
Iran has played up this year's anniversary as 40 is symbolic of maturity in the Islamic tradition and the age at which Prophet Mohammed received revelations from God.
Despite 10 days of annual celebrations launched on February 1, today's Islamic Republic faces acute economic challenges as it struggles with a mix of domestic hardships and US sanctions.
The rial has sharply devalued against the dollar, driving up prices, while the reimposition of sanctions has blocked foreign investment and limited Iran's oil sales.
In response Iranian authorities have warned against "infiltrators" who would threaten the country from within and called for "national unity".
Iran is also grappling with an environmental crisis, brought on by a mix of air pollution, soil erosion, drought and desertification.
The country has "progressed in many areas in 40 years", its environmental organisation head Isa Kalantari has said, singling out the sectors of health, industry, services and education.
But its environmental track record is simply "indefensible", he warned.
On the military front, a source of pride for Iran, it has timed two arms exhibitions in Tehran to coincide with the anniversary and showcase its latest equipment and capabilities.
At shows dubbed "40 years of defensive achievements", Tehran has unveiled a new made-in-Iran cruise missile which it said had been "successfully" tested.
Washington and its allies accuse Tehran of working to enhance its missile capabilities, threatening the whole Middle East, although Iran insists its weaponry is solely for defensive purposes.
Billboards boasting of the revolution's achievements have sprouted all across Tehran, ranking Iran first in "peaceful nuclear research in the Middle East", ninth in the world in the number of books published
each year, and fifth in "cyberspace security".
In a show of technological progress, Iran last month launched a satellite called Payam (message in Persian) but it failed to reach orbit.
Speculation is mounting that Iran could launch another domestically-manufactured satellite during the final phases of the annual celebrations.
Iran's supreme leader, the late Khomeini's successor Ayatollah Ali Khamenei, has agreed to pardon a "large number" of prisoners for this year's anniversary, according to state television.
Judiciary chief Sadegh Amoli Larijani, quoted in the Iranian media, has put at 50,000 the number of prisoners to be released.
Iran held over 217,000 prisoners in March 2017, according to official figures from the judiciary.