Raiding among cattle-herding tribes is a traditional part of life in South Sudan, but in the past five years, the skirmishes have become more violent and unrestrained. Small armed bands that traditionally guarded their communities’ livestock have been drawn into bitter proxy battles between the country’s two largest tribes: the Dinka, who hold power in Juba, the national capital, and the Nuer. No longer limited to raiding each other’s villages and herds, these bands of well-armed tribal fighters have carried out massacres and atrocities, with women and children increasingly among the victims. The violence has worsened in both scale and frequency since 2013, according to South Sudanese who have witnessed the ravages of a civil war that started just two years after their country gained independence from Sudan.The continued rise of local factions throughout global conflict zones, like these young Dinka and Nuer fighters in South Sudan, is a growing problem for humanitarian workers. “We’ve seen more nonstate armed groups emerge in the last seven years than in the previous 70 years,” says Brian McQuinn, an adviser on nonstate armed groups for the International Committee of the Red Cross and co-author of a new I.C.R.C. study on the topic. “All of these new groups that are emerging are structured in different ways.” For the most part, they are looser, with less top-down control. “The complexity of that is off the scale.” This causes a problem for humanitarian organizations whose standard method has been to go to the top commanders of a military or militia group, advise them on international humanitarian law and rely on the chain of command to enforce the rules throughout the ranks.In this new labyrinth of nonstate and state-sponsored fighters, humanitarian workers have a harder time reaching wounded soldiers and civilians and protecting their own staff members. They are also finding it more challenging to teach the nonstate fighters about the Geneva Conventions and how those laws of warfare should apply to them. To tackle the problem, the report calls for humanitarian workers to adjust their approach and use cultural references to advocate for more ethical standards of warfare.Noninternational conflicts have increased to more than 70 from fewer than 30 in just 15 years, from 2001 to 2016, according to the I.C.R.C. Of those, nearly half are waged by more than two opposing forces and sometimes as many as nine. Another 22 percent of conflicts involve 10 or more groups and, for many of them, the struggle for power is tangled with religious, ethnic or territorial agendas.“We’re seeing a high level of fragmentation,” says Clionadh Raleigh, director of the Armed Conflict Location and Event Data Project, a nonprofit conflict-research organization specializing in Africa, the Middle East and South Asia. “There has been a loosening of rules around violence generally, a loosening of order.”Some conflicts have involved hundreds of armed groups. By the end of the uprising that toppled Muammar el-Qaddafi of Libya in 2011, 236 fighting groups were known to be operating in the city of Misrata. In Syria, according to data provided by the Carter Center, the conflict has spawned more than 1,000 armed factions. In conditions like these, it becomes especially critical for humanitarian organizations to inculcate a “culture of restraint.” The I.C.R.C. study outlines ways that humanitarian organizations can make the laws of war comprehensible to the growing number and variety of armed groups, ranging from the cattleherders who take community matters into their own hands in South Sudan to roving units of young jihadists vying for influence in local politics in Mali.In the example of the Dinka cattle herders, the young men who coalesce into armed bands first bond at a young age in cattle camps, and though they serve the state’s interests at times, their primary loyalties are to their own small communities and the brotherhood formed while guarding their people’s livestock. “A lot of your life is coming and going to that physical space of the cattle camp,’’ says Naomi Pendle, a researcher at the London School of Economics, who has worked with the Dinka and Nuer. “That becomes your principal social unit, but you also fight alongside those people.” The tribes’ tight social bonds make humanitarian infiltration more difficult. Groups like the I.C.R.C. have to compete with an array of other influences as they strive to set the rules of conflict.These influences include South Sudanese military elites who sometimes offer animal vaccinations or ammunition to the cattle herders in exchange for loyalty, or chiefs who preside over the traditional courts and set the norms that determine what’s considered right and wrong within the community. Religion also plays a role in shaping the currents of local conflicts. The Nuer fear being cursed if they go against the word of local prophets, who sometimes manage to prevent them from raiding a neighboring settlement’s cattle. All these influences can provoke or restrain the bands’ use of violence. Rather than circumvent these influences, the I.C.R.C. found tapping into them was a more effective way to introduce the tenets of humanitarian law. Asking about the rules of wrestling matches that are an important source of status and prestige for young Dinka men, researchers learned that women, old men and children were not allowed to compete. They were considered too weak to participate in the sport. I.C.R.C. staff seized on this cultural norm as an analogy that could be used to teach the militants: civilian noncombatants in war were compared to the weak and elderly who would never be allowed to wrestle.Including the case study of the Dinka and Nuer, the report presents humanitarian groups with a selection of four distinct categories to describe different ways that armed groups can be structured, and suggests ways to navigate each. The strategies are a departure from the traditional approach of meeting with top commanders and outlining international humanitarian law. More organic and culturally specific approaches, the I.C.R.C. proposes, like using the wrestling analogy, can appeal to new combatants on common ground that’s already familiar to them.The report, titled “The Roots of Restraint in War,” is being released on June 18.