DOBRA, Slovakia — 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.

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As President Vladimir Putin of Russia vows to fight the war to its “full completion” and his forces regroup for an expected push in Ukraine’s east, NATO countries, including the United States, are scrambling to keep the weapons flowing and bulk up the country’s defenses.

Bolstering Ukraine’s long-range air defense capabilities is seen as especially critical. Ukraine already had its own S-300 and other air defense systems, but some of these have been destroyed, leaving Russia with a large degree of freedom to hit Ukrainian targets from the air with warplanes and cruise missiles.

Increasingly desperate to reverse this imbalance, President Volodymyr Zelenskyy of Ukraine has repeatedly pleaded with NATO to “close the sky over Ukraine” by imposing a no-fly zone. But NATO has been unwilling to send its own warplanes into Ukraine.

Instead, the United States offered Slovakia, a fellow NATO member, a substitute battery of U.S.-made Patriot missiles if it would “donate” its aging S-300 system to Ukraine.

(editor：)