Hundreds of thousands of Iranians took to the snowy streets on Monday (February 11) to celebrate the fortieth anniversary of the Islamic revolution.
Their message: "Death to Israel, Death to America".
Soldiers, students, clerics and black-clad women holding small children, flocked to the streets of cities and towns.
Nationwide rallies shown on state TV were held to mark four decades since the fall of the Shah and the triumph of Ayatollah Ruhollah Khomeini - the Shi'ite cleric who led the revolution that continues to rattle the West to this day.
On the 11th of February, 1979, Iran's army declared its neutrality.
That paved the way for the collapse of the U.S.-backed monarch - at that point the United States' closest ally in the Middle East.
Addressing the crowds on Monday, President Hassan Rouhani said Iran was determined to expand its military power and ballistic missile program.
Despite mounting pressure from hostile countries to curb Iran's defensive work, state TV reported.
The large turnout in the state-sponsored rallies comes as Iranians face rising prices, food shortages and high inflation that have triggered waves of protests.
U.S. President Donald Trump pulled out of Iran's 2015 nuclear deal with world powers last year.
He re-imposed sanctions on Tehran, which hit the country's economy.
Iranian officials claim the move amounted to "economic warfare".
Supreme leader, Ayatollah Ali Khamenei, said last week that "death to America" meant death to Trump, his policies and his lieutenants.
Saudi Arabia and other Arab countries have viewed Iran with great suspicion since the Islamic Revolution swept the Shah from power.
They feared Khomeini would inspire Islamic militants across the region.