This Monday marks the Muslim holy day of Ashura, a day that is perhaps nowhere more ardently commemorated than in Iran. The only way to fully understand what this day means to so many Iranians is to delve into a history that has repeated itself there for years on end. From the Constitutional Revolution of the early 20th Century to the 1979 Islamic Revolution to the growth of the opposition Green Movement since 2009 to last week’s storming of the British Embassy, the history of Ashura is reflected in every struggle against injustice in Iran. Whether opposing monarchy, imperialism, theocracy or crippling sanctions, the history of this day holds a unique position in the hearts of countless Iranians.

Growing up in Iran, no matter your faith or circumstance, you will learn the story of Karbala, if only because every year you will get a holiday from school on Ashura and witness countless men fill the streets in a parade of tears and self-flagellation. You will watch or possibly even join in as these devout and distinctly Iranian Shi’a Muslims pound their chests and fill the air with impassioned invocations and chants of “Ya Hussein.” Amid this mourning, there will be a unique and fervent enthusiasm, for it was on this day, some 1,300 years ago, that Imam Hussein stood tall and strong in the face of oppression, against insurmountable odds.

You cannot understand the role of Islam in Iran without knowing the story of Karbala, nor can you underestimate its influence.

On the 10th of the month of Muharram, in the 61st year of the Islamic Calendar (680 ACE), in the city of Karbala, some 100 kilometers southwest of Baghdad, Imam Hussein (the grandson of the Prophet Muhammad and the third Imam of Shi’a Islam) was savagely slaughtered in battle and rose to martyrdom.

The Battle of Karbala was the result of Imam Hussein’s attempt to liberate the people of the region from the tyrannical rule of the second caliph of the Ummayad Caliphate, Yazid I. The most popular version of the story goes like this: Over the days preceding his martyrdom, Imam Hussein and his small caravan of friends and family were surrounded by Yazid’s army of thousands. They were ultimately forbidden access to water, and on the tenth day (Ashura), Yazid’s army attacked in full force, killing all 72 of Imam Hussein’s closest companions, including his six-month old son. The final and most brutal casualty of Karbala was Imam Hussein himself, who sustained countless unimaginable wounds from arrows, stones and swords before his throat was cut while he was prostrating before the Lord in prayer. Thus, on that day, Imam Hussein rose as a martyr and has remained so for over a thousand years.

So, what does this story have to do with modern-day Iran and Iranians? Everything.

For the vast majority of Iranians who identify as Shi’a and even for many who don’t, the story of Karbala lies at the heart of all struggles against oppression and tyranny–personal and political.

In 1979, Yazid’s army was that of the Shah, the SAVAK (his vicious secret police and intelligence service), and the British and American imperialism they represented to Iranians. The Islamic Revolution was, if nothing else, a grand morality play of the Battle of Karbala on a world stage, with Ayatollah Khomeini and his cronies claiming the roles of Imam Hussein and his caravan respectively.

But while the Shah was defeated in 1979, the forces that defeated him–the mullahs, ayatollahs and masterminds of the Revolution–would soon come to take the Shah’s place as yet another symbol of the army of Yazid, all the while disguising themselves as friends of Imam Hussein. Thus lives today’s incarnation of Yazid’s army in Iran–an army of traitors, formerly part of Imam Hussein’s caravan, who are now just as brutal and oppressive as Yazid himself.

So, who plays the role of Imam Hussein’s crew in Iran’s latest production of the political passion play of Karbala?

Without a doubt, it is the Iranian people themselves-and more specifically, the members of the pro-democracy, opposition Green Movement who took to the streets after the fraudulent 2009 presidential election. The protests during that summer–after Mahmoud Ahmadinejad claimed victory in the polls before all the votes were counted–were more than a cry for justice and democracy. They were yet another production of the Battle of Karbala, with the people on the side of Imam Hussein and the traitorous regime on the side of Yazid.

As the world watched, the so-called Islamic Republic brutally suppressed the opposition during and after the protests, and it continues to torture, imprison and hang opposition activists today. In the process, it seems to have intimidated the Green Movement into submission. By all appearances, it looks as if Yazid’s army, led by the mullahs and ayatollahs and their Revolutionary Guards and courts, has prevailed. But appearances can be deceiving, especially in Iran. Something is still brewing, and as Iran’s disproportionately young population continues to grow up under this suffocating regime, it is yet again drawing from the lessons of Karbala. Iran’s freedom fighters will re-emerge with these lessons in mind; bringing a larger, louder and wiser army with them. In due time-as young Iranians start having children of their own, children they refuse to watch suffer the same indignities-they will honor Imam Hussein and win back their God and country once and for all.

Melody Moezzi is a writer, attorney, activist and award-winning author. She is also a United Nations Global Expert with the UN Alliance of Civilizations and an Opinion Leader with the British Council’s “Our Shared Future” initiative.