US President Donald Trump’s announcement that Ukraine will receive Patriot missile systems as part of a new package of US weaponry has been warmly welcomed in Kyiv as it reels under nightly Russian bombardments.

Ukraine is getting more US Patriot missile systems to counter Russian attacks. Here’s what they are, how they work, and why Kyiv says they’re urgently needed.

The president announced the US will send additional Patriot air-defense systems to Ukraine, part of a European Union–funded deal.