The exercise, known as Hedgehog 2025, involved more than 16,000 troops from 12 NATO countries who drilled alongside Ukrainian drone experts, including soldiers borrowed from the front line. It simulated a “contested and congested” battlefield with various kinds of drones, says Lt. Col. Arbo Probal, head of the unmanned systems program for the Estonian Defence Forces. “The aim was really to create friction, the stress for units, and the cognitive overload as soon as possible,” he says. That tests the soldiers’ ability to adapt under fire.