The last remaining nuclear arms pact between Russia and the United States is set to expire this week, removing any caps on the two largest atomic arsenals for the first time in more than a half-century. The end of the New START Treaty sets the stage for what many fear could be an unconstrained nuclear arms race. Russian President Vladimir Putin has declared his readiness to stick to the treaty's limits for one more year if Washington follows suit, but U.S. President Donald Trump has been noncommittal about extending it. Arms control advocates have warned that the treaty's termination would fuel a renewed arms race.

Russia has launched a massive overnight attack on Ukraine, using hundreds of drones and dozens of missiles. Officials say at least four people have been killed. For only the second time in the nearly 4-year-old war, it used a powerful, new hypersonic missile that struck western Ukraine in a clear warning to Kyiv's NATO allies. The attack came days after Ukraine and its allies reported major progress toward agreeing on how to defend the country from further aggression by Moscow if a U.S.-led peace deal is struck. The attack also coincides with a new chill in relations between Moscow and Washington over Venezuela and the U.S. seizure of one of its oil tankers in the North Atlantic.

Russia's nuclear-capable Oreshnik missile system has entered active service, Russia's Ministry of Defense says, as negotiators continue to search for a breakthrough in peace talks to end Moscow's war in Ukraine. Troops held a brief ceremony to mark the occasion in neighboring Belarus where the missiles have been deployed, the ministry says. It did not say how many missiles had been deployed or give any other details. The announcement comes at a critical time for peace talks, with negotiators still searching for a breakthrough on key issues, including territory and control of the Zaporizhzhia nuclear power plant.

The coming week could be pivotal in the ongoing war between Russia and Ukraine. U.S. President Donald Trump's special envoy, Steve Witkoff, is expected in Moscow midweek. Trump has set a Friday deadline for Russia to stop its aggression or face severe economic penalties. The diplomatic stalemate remains challenging, with Ukraine losing territory but showing no signs of a defense collapse. Trump has expressed skepticism about the effectiveness of sanctions, while Russia continues its military advancements. The conflict has resulted in significant civilian casualties, with over 12,000 Ukrainian civilians killed according to the United Nations.

Kyiv is observing a day of mourning after a Russian drone and missile attack killed 31 people, including five children, and injured over 150. The attack on Thursday marked the highest number of child casualties in a single strike on the city since October 2022. It was also the deadliest attack on the city since July last year, when 33 were killed. The Russian assault destroyed a large part of a nine-story residential building and damaged over 100 other structures. Ukrainian President Volodymyr Zelenskyy has called for stronger sanctions against Russia. Meanwhile, Ukrainian forces are under pressure in the eastern city of Chasiv Yar as Russia pushes to break through Ukraine's defenses there.