Russia's war in Ukraine is increasingly spilling beyond its borders. From suspected sabotage and cyberattacks to drones and aircraft testing NATO airspace, Moscow is probing how far it can go without triggering a wider confrontation. Meanwhile, uncertainty over US support is forcing Europe to rethink its own defenses. But with 27 EU countries divided by competing priorities and far-right, nationalist politics gaining ground across the continent, can Europe agree on how to respond? Ian Bremmer explains why Vladimir Putin's biggest test for Europe may be whether the continent can act together before a crisis forces its hand.