President Emmanuel Macron is updating France's nuclear deterrence doctrine as Europe worries about Russia and doubts U.S. protection under Donald Trump. On Monday, Macron will speak at a French submarine base and signal how France thinks about using nuclear weapons. The war in Ukraine and Russia's nuclear threats have shaken Europe's security assumptions. Analysts say some Europeans are looking to France for a backup nuclear guarantee. France is the only nuclear power in the European Union. Macron last laid down policy in 2020 and said France has fewer than 300 warheads. Experts are listening for any stronger promise to protect allies.

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.

President Donald Trump has declined to say whether he plans to resume underground nuclear detonation tests. He had seemed to suggest that was a possibility in a social media post this week. The post raised concerns the U.S. would begin testing nuclear weapons for the first time in three decades. The president told reporters, "You'll find out very soon" when he was asked about it. Trump said, "We're going to do some testing" and "Other countries do it. If they're going to do it, we're going to." But he refused to offer more details. He spoke aboard Air Force One as he headed to Florida on Friday for the weekend.

President Donald Trump has appeared to suggest on social media that the U.S. resume testing nuclear weapons for the first time in three decades. There was no indication that the U.S. would start detonating warheads, but the president offered few details about what seemed to be a significant shift in U.S. policy. He made the announcement on social media minutes before meeting with Chinese leader Xi Jinping on Thursday in South Korea. The U.S. military already regularly tests its missiles that are capable of delivering a warhead, but it has not detonated the weapons since 1992 because of a test ban.

The Tomahawk cruise missile has been in the U.S. military's inventory since the 1980s. While slow by missile standards, the cruise missile flies around 100 feet (about 30 meters) off the ground, making it harder to detect by defense systems. The missile also boasts an impressive range of around 1,000 miles and precision guidance systems that make it the go-to weapon for striking targets that are deep inland or in hostile territory. President Donald Trump has hinted that he might give Tomahawks to Ukraine, which could make a key difference for Kyiv in its war with Moscow. While the United States launched Tomahawk missiles almost exclusively from ships or submarines, Ukraine doesn't possess a Navy with ships capable of carrying the 20-foot-long missile.