Geo-politics shifted dramatically with the Russian invasion of Ukraine in February 2022. This major escalation of the Russo-Ukrainian War, which had started in 2014, drew in the United States, most of Western Europe, and their allies around the world. Meantime, Russia strengthened its ties with China, North Korea, Iran, and others in Asia and the Global South. There was a resultant split in the UN Security Council and deepening global division along the lines of prior conflicts in Asia, Africa, and the Middle East. The belief that large scale warfare between developed states had been consigned to history vanished with the return of trench and tank warfare reminiscent of the First World War, and this combined with the newer technologies of drones, cyber, and artificial intelligence. The nature of war remains the same - one side tries to force its will on another which resists with reciprocal military force - but the character of war is changing dramatically. The character of peace-making is being forced to adapt to the new situation. International structures that facilitated negotiations are dissolving and those who sought to lead through resolving conflicts have been replaced by those who lead in conducting conflicts. The 10th Annual Conference on the Resolution of Intractable Conflict held at Oxford University in September 2023 drew experts from across the globe to address The Changing Character of War and Peacemaking and in this book the New England Journal of Public Policy and ARTIS Europe Ltd have published the best papers from that meeting.