Putin is testing NATO's defenses. How will it respond?

U.S. allies called an emergency meeting of the United Nations Security Council on Monday after a series of incidents raised alarm about Russian threats to NATO.

Drones over Poland. Fighter jets above Estonia. Surveillance planes over the Baltic Sea.

To U.S. allies in Europe, the pattern is unmistakable: A deliberate campaign of escalation from the Kremlin, designed to probe NATO’s defenses and political resolve.

The question hanging over an emergency meeting of the United Nations Security Council on Monday is how exactly the alliance will respond.

As NATO struggles to turn alarm into action, officials and analysts urged a more forceful response and warned that hesitation risks emboldening Russian President Vladimir Putin. But questions about U.S. support, escalation risks and what this growing threat means for Ukraine remain unresolved.

Estonia, which called for the Security Council meeting after three Russian MiG-31 fighter aircraft entered its airspace for 12 minutes without permission last week, pressed members to address what it described as a “blatant, reckless, and flagrant violation of NATO airspace” and Russia’s “repeated violations of international law.”