Russian drones tested NATO's air defenses across Europe all summer, and the alliance did not do well — bad news for Europe's sense of security heading into autumn.

• Russian drones crossed into NATO airspace week after week, hitting Poland, Romania, the Baltics, Belgium, the Netherlands and Germany.
• The goal was not destruction but probing — measuring how fast each country reacts and what weapons it has ready.
• Sixteen NATO countries have now had drone incursions, spreading far beyond the old excuse of spillover from Ukraine.
• At a German cargo airport, an explosive drone was flown into a Ukrainian transport plane; the charge failed to go off.
• Each country still has its own rules on when to shoot, so responses have been slow and inconsistent — one drone Romania declined to fire on crashed into an apartment block and hurt a woman and a child.

Outlook: Europe is rushing to build a shared "drone wall" of cheap sensors, but Russia is already fielding faster jet-powered drones and the American troop commitment looks shakier than ever.