The North Atlantic Treaty Organization’s European nations would need to bolster standing militaries by at least 300,000 troops and significantly boost defense spending beyond 3.5 percent of gross domestic product—at least 250 billion euros—while reviving and integrating their industrial base to defend themselves against Russia without the United States.
And they’d need to do that fast, according to a 2025 joint analysis by European think tanks Bruegel and the Kiel Institute for World Economy.
