Ukraine is pursuing a multibillion-dollar arms buildup that would be funded by Europe, seeing it as the best chance of ensuring the country’s long-term survival as American assistance dries up and Western security guarantees remain uncertain.

Kyiv wants not only to sustain its army through the current war but also to make it the backbone of any postwar settlement, with the goal of deterring Russia from invading again. As Ursula von der Leyen, the European Commission president, recently put it: “Ukraine must become a steel porcupine, undigestible for potential invaders.”

At the center of these efforts is a new NATO-backed procurement system that will channel European funds into buying U.S. weapons for Ukraine. President Volodymyr Zelensky hopes the system will enable $1 billion in purchases each month, with a particular focus on acquiring U.S.-made Patriot air-defense systems to expand Kyiv’s limited arsenal.

The new system would both help replace U.S. arms donations that President Trump has ended and also increase and streamline deliveries of weapons to Ukraine over time. A first sale of cruise missiles and GPS navigation kits, worth $825 million, was announced on Thursday.

Kyiv is also betting on its booming domestic defense industry, which has already delivered drones that swarm the battlefield and is now working to produce more powerful weapons. This month, Ukraine said it had completed the development and begun production of its first domestically made long-range cruise missile.

How far this military buildup can go remains uncertain. European nations that are already grappling with budget strains may struggle to sustain the level of funding Ukraine says it needs, and Kyiv’s army must address persistent manpower shortages to become a truly deterrent force.