3The Brief15The View22Winter OffensiveTo prevent Putin from going nuclear, Ukraine must continue the fightBy Elliot AckermanPlus: Biden’s strategyBy Graham Allison28NuclearMomentBeatrice Fihn, who won a Nobel for campaigning for global disarmament, meets a perilous turning pointBy Naina Bajekal32Building a Better Bomber The stealthy and very expensive B-21 Raider heralds a new era of great-power confrontation By W.J. Hennigan38FarmingIn the Forest Agroforestry offers both a lifeline for Brazil’s troubled agriculture industry and an alternative to clear-cutting the AmazonBy Ciara Nugent44A Happiness GuideThe founders’ pursuit By Darrin M. McMahon How the happiness professor battles burnout By Jamie DucharmePlus: Joy-building tips from experts 57Time OffWorkers take a water break while planting tree seedlings in Timburi, BrazilPhotograph by Victor Moriyama for TIME