IN RECENT WEEKS Ukraine has endured some of the most intense drone and missile bombardments since the start of Russia’s full-on invasion three years ago. There could scarcely be a worse time for America to halt the delivery of precious air-defence equipment. Yet Ukrainian officials say that on the night of June 30th-July 1st the Pentagon turned back cargo planes delivering supplies of air-defence interceptors and other arms to European bases, from where they would be taken overland to Ukraine.