This week in Jeddah, the leaders of Ethiopia and Eritrea signed a peace deal that seeks to draw a line under two decades of hostilities. It’s a stunning and momentous turnaround in the relationship between the neighbors. Until recently, they had been locked in a bitter border dispute, in which up to 100,000 had been killed and thousands displaced. But then, in April, a new pro-peace prime minister, Abiy Ahmed, took office in Ethiopia and sought to heal the rift with Eritrea by accepting an earlier ruling on the disputed border. Events have moved swiftly since then, with trade and diplomatic relations restored, and borders reopened. The peace deal is a cause for celebration among Ethiopians and Eritreans, who can now speak to each other on the phone, visit relatives and friends, and do business with each other after years of separation. It’s also a significant advance for those concerned with global peace and security. The end to one of the Horn of Africa’s major conflicts should increase stability and economic growth prospects in the wider region, as well as provide hope to those seeking to solve seemingly intractable conflicts elsewhere in the world. As the international community marks UN World Peace Day on Friday, it can celebrate the long-term decline in state-on-state confrontations across the world, such as the one between Ethiopia and Eritrea. It’s also a time to focus on the work that needs to be done to make peace last. A peace agreement does not automatically lead to peace — many of today’s conflicts in Africa are ones that resumed after previous peace deals broke down. Saudi Arabia and the UAE brokered the deal between Ethiopia and Eritrea, and their ongoing support will be essential to its successful implementation Alison Baily So, how can Ethiopia and Eritrea make their deal hold? Lessons from elsewhere on the continent show that success depends heavily on the leaders themselves. They need to show strong commitment to implementing the agreement and making the difficult compromises involved, often in the face of opposition from within their own camp. To rally their people behind the deal, they also need to present a powerful vision of the future that peace can bring. Secondly, strong and effective institutions are needed to fulfill the terms of the peace agreement and address the root causes of conflict. Thirdly, and most critically, wider society needs to feel the benefits of peace in their own lives, through improvements in security, freedoms, and the new job opportunities created by the increased investment and trade that peace can bring. If they do not, then grievances could grow and put pressure on their leaders to pull out of the agreement and resume fighting. Finally, outside support is key. Influential third countries and international organizations such as the African Union and UN can act as guarantors of the agreement and provide oversight, particularly in its fragile first few months. Saudi Arabia and the UAE brokered the deal between Ethiopia and Eritrea, and their ongoing support will be essential to its successful implementation. International aid and investment will help underpin the peace by boosting post-conflict recovery and economic growth. Translating conflict into sustainable peace is a challenging and long-term process that can take a generation. But, if all these factors are in place, then the prospects for success will be good. If just one is missing, then the peace will always be fragile. Hopefully for Ethiopians and Eritreans, the dividends of peace will mean that their 20-year war will quickly become consigned to the history books. Alison Baily is an international affairs analyst, specializing in the Middle East and Africa.