Driving back to his village near the Ukrainian border last Thursday, the mayor had to stop to let a train pass, and assumed he wouldn’t have to wait long. But the flatbed wagons, stacked high with military equipment, just kept coming. He waited for nearly half an hour.

"It was a very long train, much longer than usual,” recalled Mikolas Csoma, the mayor of Dobra, a previously sleepy village in eastern Slovakia that, over the past month, has become a key artery funneling weapons and ammunition into Ukraine by rail from the West.

The train that delayed Csoma’s drive home was not only unusually long but also signaled a singular escalation in Western efforts to help Ukraine defend itself. It carried an air defense system made up of 48 surface-to-air missiles, four launchers and radars to guide the rockets to their targets, which in Ukraine means Russian warplanes and missiles.