Twelve years ago, when I lived in Aden, protests by the Southern Movement were a regular occurrence — and with equal regularity, they were brutally suppressed. The complaint of the Movement was this: that the unification of Yemen in 1990 had been carried out with a promise of parity between North and South, but this had failed to materialize. When I left Yemen — young, naive and overconfident of my analytical prowess — I predicted a civil war within three years. But, like many, I was thinking about a re-run of the civil war of 1994: a north-south clash over the steamrollering of the promises made four years earlier. The South lost that one, and northern dominance of the economy and government of Yemen grew apace. But while the troubles that began in 2011 were not triggered by the Southern Movement, the legacy of 21 years of broken promises is hard to erase. It is that legacy that we have seen played out in blood on the streets of Aden this week. Once again, we can only wonder what might have happened if only the transitional process that started in 2011 had been left to run its course. The National Dialogue was intended, through democratic means, to settle the future of Yemen and address the grievances that built up over the three decades of Ali Abdullah Saleh’s rule. That hope of resolving the southern issue was taken away by the Houthi coup in 2014. Now, with five years of bitter fighting under their belts, certain separatist factions in the South have decided they have waited long enough. The cost to Yemen is bitter and costly enough as a result of the war currently being fought, the lives that have been lost and the legacies of the conflict: fields of landmines, devastated infrastructure and broken communities. We can only hope for the future of Yemen to be placed in the hands of its people. But any just resolution is even further off when there is war within a war — and historical experience demonstrates that, in the words of President Lincoln: “A house divided against itself cannot stand.” While the anti-Houthi forces argue and fight over control of this city or that, the Houthis themselves have not been defeated. Peter Welby Although in retrospect the achievement of victory in war seems obvious, in the moment it is not. While the anti-Houthi forces argue and fight over control of this city or that, the Houthis themselves have not been defeated. The squabbling factions are like the owners of a stolen cow arguing about who should drink the milk. Meanwhile, the outside world watches in bewilderment. The sterling efforts of Yemenis to convince the world that they are engaged in a just war against the forces of theocratic tyranny are dealt blow after blow by incidents such as these. No one disputes the fact that the legitimate government of Yemen does not have a perfect record. Nor is there any dispute that the grievances felt by those parts of South Yemen represented by the Southern Transition Council (STC) are genuine. In some parts of the South, including Aden, there persists a security challenge from groups such as Daesh and Al-Qaeda, as well as from bandits. Regrettably, in a speech on Sunday the president of the STC appeared to blame terrorist attacks — and even a Houthi attack that killed a senior military officer — on the government. This is not going to solve any of the issues facing Yemen, North or South. Security will only be restored to territory liberated or secured from the Houthis if all of the factions are working together. While Aden suffers, both sides have appealed to Saudi Arabia to mediate. Given the Kingdom’s own strong interest in securing the defeat of the Houthis — a course of action to which both the government and the STC remain committed — this commitment to engage in mediation is a positive sign of the continued focus by the factions on the true goal. Civil war is never simple — there are too many competing interests and desires within a country. This is not only obvious from recent experiences in many countries in the Middle East and North Africa, but from historical experience around the globe. Ego and vanity lead to courses of action against one’s allies in ways that can prove deeply harmful to the cause. Being on the side of right does not guarantee victory; only unity, sound strategy, and discipline can achieve that. Fragmentation and factionalism not only make victory unlikely, they are likely to extend the war and exacerbate the suffering of the Yemeni people. There is one goal that matters in Yemen: to demonstrate conclusively that private interests cannot succeed by force of arms. The Houthis’ mistake was to believe that their own factional desires justified starting a war. They must be shown the error of their ways. When that has happened, Yemen will require a new political settlement. The years of war since 2014 have changed the country; the sound conclusions of the National Dialogue Conference will need to be revisited. There will be ample opportunities for the STC to make its case at that point. There will also be opportunities for new elections, renewing the legitimacy of the national government. But Yemen will only reach that point if the forces fighting the Houthis remain united. In the flush of victory over the Houthis, space will be created for a generous and imaginative national settlement. I hope that the words of the STC leadership, and of Yemen’s government, supporting Saudi Arabia’s mediation will be matched by actions that restore unity. Because that is the only way that Yemen’s war will be won.