Iranian students run from tear gas during a demonstration at the University of Tehran on Dec. 30. (Agence France-Presse via Getty Images)

Maria J. Stephan directs the Program on Nonviolent Action at the U.S. Institute of Peace and is co-author ofWhy Civil Resistance Works: The Strategic Logic of Nonviolent Conflict.”

The breadth and depth of the protests in Iran, which began on Dec. 28 in response to popular dissatisfaction with the poor economy and political repression in the country, are posing a serious challenge to the Islamic republic. There have been marches and lightning protests in dozens of cities, towns and villages across the country. Businesses have gone on strike to protest regime corruption. A new Twitter hashtag, “if there was no Islamic Republic,” is prompting Iranians to envisage an alternative future without a theocracy.

Not surprisingly, the Iranian regime, initially caught off guard by the wide-ranging protests in traditionally pro-government areas, has cracked down hard. At least 21 people have been killed and at least 1,000 arrested. (The real number of those detained is probably much higher.) Most of the dissent has been nonviolent, though there have been some attacks on regime security personnel. Even so, the level of brutality exacted by the regime far exceeds that of the protesters. But there is a good reason for the opposition to avoid violent escalation. Its ability to achieve significant political change will be greatly enhanced if it maintains nonviolent discipline.

It is understandable that unarmed people facing live bullets, arrests, beatings and torture would respond with violence. Yet there is little evidence to suggest that turning to violence, or mixing violent and nonviolent tactics, will either protect civilians or advance the goals of those resisting. The introduction of opposition violence has been empirically shown to lower active participation in otherwise unarmed movements, particularly reducing the involvement of women, the elderly, the disabled, the marginalized and otherwise at-risk groups. This is highly problematic, as research also shows that the size and diversity of participation in nonviolent struggles is the most important variable in determining the outcome. It is hardly surprising that governments use agents provocateurs to infiltrate nonviolent movements and foment opposition violence, because this allows them to justify a violent and forceful response.

Nonviolent discipline by protesters not only encourages participation. It encourages loyalty shifts and defections within key pillars propping up the regime, notably the security forces. Conscripts and foot soldiers are typically more likely than officers to disobey orders to shoot at peaceful protesters. In 2009, during the so-called Green Movement unrest, there was a large social distance between the mostly Tehran-based, wealthier protesters and the security forces. Now, however, that distance has shrunk due to the large lower- and middle-class participation in the current round of protests. There have been isolated reports of Basij militia conscripts tearing up their identity cards.

The larger and more diverse the participation in the nonviolent resistance, the greater the chances that soldiers and police faced with the prospect of shooting their family members and friends will disobey orders.

Maintaining nonviolent discipline in a highly repressive place such as Iran is a challenge. Telling people they should refrain from weapons is not enough. People need to have hope and confidence that their nonviolent resistance is leading somewhere. Inside Iran, it is exceedingly difficult to meet, organize and strategize. That helps explain the leaderless nature of the current protests, which has, in turn, made it difficult for the government to stop them. While social media (and cyber-tools to evade censorship and firewalls) have made decentralized organizing possible, sustaining the nonviolent resistance will require a leadership capable of long-term planning and declaring small victories. (The average nonviolent campaign, historically, takes three years to run its course.)

Tactical shake-ups are another way to encourage nonviolent discipline. That means alternating between methods that concentrate people in the streets and those that involve dispersed actions, including stay-at-homes, go-slow actions and consumer boycotts. Tactical innovation is key to maintaining resilience and momentum — and keeping the regime off guard and increasing the geographic reach of the protests. Marches and street demonstrations are not the be all and end all of nonviolent resistance. Some of the most important work of nonviolent resistance happens off the streets, and involves coalition building, fundraising and building organizing infrastructure.

While Iranians will dictate the future of their country, outside governments can help preserve space for nonviolent protests by increasing diplomatic pressure on the Iranian regime and by coordinating targeted sanctions of individuals and entities responsible for human rights violations. Governments, international organizations and media outlets can amplify the work of Iranian bloggers and citizen journalists courageously reporting on the nonviolent resistance. They can increase support for digital and offline security protocols for activists. Diaspora groups and human rights organizations can be conduits for Farsi-language materials on strategic nonviolent action and civil resistance.

It is unclear what will come of the current uprising in Iran. But the scope and intensity of the protests suggest that the legitimacy of the Iranian regime may be eroding. The ability of opposition groups to organize, plan and maintain nonviolent discipline will help determine whether this protest moment sustains itself and leads to positive political change.