(CNN) -- As the 31st anniversary of the Islamic Revolution approaches this week, with the promise of mass protests from Iran's growing opposition movement, it's tempting to compare the upheaval with unrest that ultimately toppled the shah of Iran.
A coalition of Iranian reformist groups is urging opponents of the regime to stage nonviolent protests this week, serving as a show of force for citizens who oppose the government's stiff crackdown on those who protested Iran's disputed election last June.
While there are striking similarities between the movements separated by decades of Islamic rule, experts say there are even stronger differences that make what lies ahead for the current movement extremely challenging.
"This is a movement that isn't trying to make a revolution in the sense of toppling a regime," said Abbas Milani, director of Iranian studies at Stanford University. "It's making a revolution in trying to make a democratic change."
But first, the similarities.
The fluctuating street demonstrations that have roiled Iran since the country's disputed presidential election revive memories of the mass protests that flared up against Mohammad Reza Shah Pahlavi, Iran's last monarch.
"Taking to the streets is as Iranian as apple pie is American," said Ervand Abrahamian, author of "A History of Modern Iran." He noted that Iranians have used street protests as their weapons of choice as early as the Tobacco Protest of 1890, a revolt led by Shiite clerics against a tobacco concession granted by Iran's imperial government to Britain.
The opposition movement 31 years ago was led by the shah's nemesis, Ayatollah Khomeini. The stoic, steely-eyed religious leader was exiled from Iran in 1964 but continued to denounce the shah as a corrupt dictator and Washington's puppet. Today's so-called Green Movement has been protesting for social justice, freedom and democracy in demonstrations throughout the country since the June polls -- using slogans that are often identical to those heard during the 1979 Islamic revolution.
In both movements students were at the forefront, as was the innovative spread of anti-government rhetoric. While Khomeini's supporters circulated audiotapes of his fiery speeches throughout Iran, today's movement relies heavily on new technology, namely social networking sites like Twitter and Facebook and the popular video site YouTube.
"The present day movement is clearly anti-despotic, and it shares that feature with the movement in 1979," said Ali Banuazizi, a political science professor at Boston College.
But that's where the similarities between the two movements largely end, observers say.
Take the opposition's enemy for instance. In recent months, opposition leaders Mir Hossein Moussavi and Mehdi Karrubi have compared the violent government crackdowns against protesters to the actions of shah, whose brutal Savak police force was one of the most hated and feared elements before the Islamic revolution.
Karrubi and Moussavi, who both ran against hardline President Mahmoud Ahmadinejad, have criticized the government, saying remnants of the "tyranny" and "dictatorship" that prevailed under the shah's regime persist today.
"I think the opposition would like to see direct parallels, which make the toppling of the regime seem imminent," Abrahamian, said. "But the differences are very much different."
"The shah had very little legitimacy -- he was brought to power by a foreign-inspired coup," he added, noting that Pahlavi was restored to power after a coup led by Britain and the United States ousted nationalistic Prime Minister Mohammad Mossadegh. The shah had previously fled Iran after Mossadegh and his supporters challenged Pahlavi's control.
"The present regime, even though it lost a lot of legitimacy with the irregularities of the election and the refusal of allowing the public to express itself -- that aura of legitimacy is still there."
That's because it, unlike the shah, came to power by mass support and maintains a conservative base throughout Iran. The reformists now fighting so firmly against it -- Moussavi, Karrubi, former president Mohammad Khatami, and others -- are the same followers of Khomeini who helped usher in the Islamic Revolution that now serves as the backbone of the government.
What they are demanding is the democratic system promised by Khomeini. The uprisings are rooted in the June election, when opposition leaders called Ahmadinejad's overwhelming second-term win a fraud. "Where is my vote?" became a common slogan in the protests.
Part of the government's strength is its well-organized security forces -- posing brute strength to counter the protesters -- that answer straight to Iran's current supreme leader, Ayatollah Ali Khamenei. Iran's Revolutionary Guard Corps (IRGC) was established after the 1979 Islamic Revolution to defend the regime against all threats, "but has since expanded far beyond its original mandate," according to the Council on Foreign Relations, a U.S. foreign policy research center.
"Today the guard has evolved into a socio-military-political-economic force with influence reaching deep into Iran's power structure," the CFR says, noting that several current and former IRGC members have been appointed to positions as ambassadors, mayors, undersecretaries, provincial governors and cabinet ministers.
During the demonstrations that followed the election, the IRGC's paramilitary volunteer force -- the Basij -- was seen chasing protesters on motorcycles and attacking them. Amateur videos showed members of the Basij, wearing plain shirts and pants and wielding clubs and hoses, dispersing protesters and beating a handful of Iranians at a time.
"Today, Iran's security apparatus is entrenched in the Islamic republic," said Hamid Dabashi, professor of Iranian studies at New York's Columbia University. "Over the last three decades, what the Islamic republic has done instead of investing in jobs, is invest in security."
Also, the opposition leadership, though fervent supporters of Khomeini, is quite different from the late charismatic leader who was regarded as an "imam" -- a title bestowed only on those believed to be anointed by God.
Still, crushing dissent became a trademark of Iran's regime after the revolution, as Khomeini returned to install strict Islamic rule as opposed to the true democracy many of his supporters had bargained for. According to Amnesty International, the regime secretly executed up to 5,000 political prisoners in 1988. Morality police even patrolled the streets in a campaign against Western-styled clothing, music and behaviors.
Today's opposition leaders are "nominal leaders, put there by the people -- but none of them are willing to risk people's lives," said Milani. "If Moussavi was as reckless with people's lives as Khomeini, he could have challenged this regime much more."
The makeup of today's protesters -- youth, women, teachers, reformists -- also lacks a key component that helped bring down the shah: labor workers.
"There were very strong labor strikes -- that's what really broke the back of the old regime," Milani said. "We know from documents that when the oil industry when on strike, the regime had no choice"
Experts agree that there's been no significant upheaval from Iran's industry workers or the merchants at bazaars.
Perhaps the greatest challenge to the Iran's current opposition movement is the sheer refusal of the government to back down. Ahmadinejad's administration, under Khamenei's watch, has vowed to respond with force against any protests during the anniversary celebrations this week. Thousands were arrested during last summer's demonstrations, and hundreds were accused of engaging in a "soft revolution" and tried in court. At least 11 protesters have been sentenced to death after the election, and a few have already been executed.
"What is different is that the shah had lost momentum, spirit and interest" toward the end of his rule, Dabashi said.
The current regime has felt blows to its credibility from the West, its senior clergy and of course, the opposition, but has shown no signs of crumbling in the face of accusations of human rights violations or bloodshed. It seems the government has grown even more defiant over recent weeks, beefing up security for the expected protests and even declaring it would enrich uranium at higher levels in defiance of demands from the United States and other Western nations.
"I think this regime at this moment is more despotic," Milani said. "The shah claimed to be the king. Khamenei clams to present the voice of God."
"If you go against the shah, you're going against the regime," he added. "If you go against Khamenei, you are 'mohareb' -- he or she who fights God."
-- CNN's Reza Sayah contributed to this report.