Thirty-one years since the downfall of the U.S.-supported Iranian dictatorship of Shah Reza Pahlavi, the Islamic Republic has developed a formula for celebrating the anniversary of the revolution. The government buses in massive crowds from all over the country, who then parade down Tehran's avenues, which are decorated with patriotic-themed paintings by schoolchildren, while crack military units perform maneuvers and politicians make rousing speeches laced with anti-American rhetoric. But this year, Iran's opposition movement wants to change the script.The opposition leadership has called on its supporters to use the occasion — which this year falls on Thursday — to continue the series of protests that began after the disputed victory of Mahmoud Ahmadinejad in the presidential election in June. But with the Iranian government's declaring in advance that no mercy will be shown to anyone who tries to disrupt the official celebrations, the stage is set not just for a battle over the streets of Tehran, but also for the legacy of the Iranian revolution.Both Iranians and the outside world will be watching how events unfold on Thursday to see just how much life remains in the opposition movement months after the government began cracking down on public displays of dissent. Knowing this, the Iranian government has spent weeks trying to prevent a large opposition turnout. Internet and text-messaging services have ground to a virtual halt, which the government has explained by citing technical difficulties but which opposition supporters say is timed to prevent them from organizing other supporters. At least 1,000 people have been arrested in the past two months, according to human-rights groups, under new laws that allow blanket detentions. Iran now has more journalists imprisoned than anywhere in the world, with at least 65 in jail, according to Reporters Without Borders. Last month, the government executed two people it claimed had participated in opposition demonstrations under the charge of waging war against God. At least nine other people accused of being opposition supporters are on death row. "We are closely watching the activities of the sedition movement," Tehran's police chief, Ismail Ahmadi-Moghaddam, said on Wednesday. "If anyone wants to disrupt this glorious ceremony, they will be confronted."With normal telecommunications blocked or censored (including reported plans to shut down Google's Gmail service and replace it with a homegrown product), opposition organizers are spreading information by word of mouth or in public places by text-messaging using Bluetooth wireless protocol, which despite its limited range is hard to block. The opposition has also asked its supporters who are too afraid or unable to attend demonstrations to gather in their gardens and release green balloons, a reference to the signature color of the opposition, which is known as the Green Movement. Other tactics proposed by organizers include joining in the official ceremonies and then switching into green clothing, or changing the meaning of government-sanctioned slogans like "Death to America" into satirical ones like "Death to Russia" or more pointed ones like "Death to the Dictator." And though some have called on demonstrators to be as peaceful and silent as possible, disruption is the order of the day. "The more overwhelming we are, the more difficult it will be for the security forces to handle us," read an opposition e-mail. Another opposition memo called on supporters to try their utmost to disrupt Ahmadinejad's planned speech.At stake in the coming clash could be the future of the Islamic Republic. What was once a spontaneous movement to contest the results of the presidential election, which opponents of Ahmadinejad say was fraudulent, has become a broader critique of the regime itself. Though most of the opposition's leaders still support Islamic government, they say the current leadership has abandoned both the democratic norms of the Republic and the moral legitimacy of Islam by abusing its own people.Meanwhile, Iran's government appears ready to confront its opponents at home and abroad. On Monday, Iran notified the International Atomic Energy Agency that it would begin enriching its uranium stockpiles to 20% concentration, from its current level of 4%. Though the government says the higher level of enriched uranium would be used to fuel a medical reactor, each step Iran takes in advancing its nuclear-development program increases international suspicion that it intends to build a nuclear weapon.The U.S., meanwhile, has responded to the failure to reach an agreement in nuclear talks by stepping up pressure on the Iranian government. The Obama Administration is preparing new sanctions against Iran's Revolutionary Guard Corps, the élite military branch that controls much of the economy, which the opposition accuses of orchestrating the post-election crackdown. But the Iranian government has in the past effectively used American and Western pressure to delegitimize internal dissent, and it is doing so again. Supreme Leader Ayatullah Ali Khamenei, who in the past has accused demonstrators of being agents of foreign intelligence services, said on Monday that the celebration for the anniversary of the revolution would be a "punch in the mouth" to the arrogance of foreign powers. Hopefully, the dispute between Iran and American will be limited to verbal fisticuffs.