NATO fighter jets were scrambled and ground-based air defense systems put on high alert in Poland and Romania during an overnight Russian attack on Ukraine.

Poland’s Chief of the General Staff, General Wieslaw Kukula, told Polskie Radio that Moscow had “begun the period of preparation for war.” He said Russian activities were shaping conditions that could enable “potential aggression on Polish territory.

Vladimir Putin told his top officials that Donald Trump's peace plan could be the 'basis' of ending the war - just before an attack on Ukraine forced NATO to scramble war planes overnight

A spokesperson for Poland's special services minister accused Russian intelligence Tuesday of orchestrating a railway blast that destroyed a key track on a route used to deliver aid to Ukraine. Jacek Dobrzyński told reporters that "everything indicates" Russian intelligence was behind the sabotage of Polish railways.

While the U.S. has taken part in previous iterations of the military exercise, this year's U.S. footprint was smaller as allied nations are pressed by the Trump administration to put more into European defense.

NATO was forced to scramble fighter jets after the Russian forces launched one of the biggest drone and missile attacks on Ukraine. At least 25 people have been killed and 75 injured – with

Romania evacuated residents after a suspected Russian drone strike hit a Turkish LPG tanker in Ukraine's Izmail port.

Business Insider observed US, Polish, and Romanian forces learning to use the Merops system, which has been combat-proven in Ukraine.

Tensions rose after a blast damaged the Warsaw-Lublin rail line, which has been used to deliver aid to Ukraine, and a Russian missile attack killed at least 25 people in Ternopil.

A drone was detected around five miles into Romanian airspace in the early hours of Wednesday morning, the country's defense ministry said.

The drone incursions and the instability on NATO’s eastern flank stem from Russia’s war in Ukraine, now approaching the end of its fourth year. The conflict has become a crucible for drone development, transforming the battlefield into a testing zone for new technology which now has applications elsewhere in Europe.

Poland said on Wednesday it would close the last Russian consulate in its territory and deploy thousands of soldiers to protect infrastructure in response to a railway explosion it blames on Moscow.