Russia is one of the biggest winners in the early days of the largest U.S. military confrontation in decades, as Iranian missiles deplete stocks of Patriot interceptors that Ukraine needs for its defense. Even before the Iran campaign, production bottlenecks in the U.S.-made Patriot system had drained Ukraine’s reserves and left European allies on yearslong waiting lists. Those shortfalls have allowed Russia to punch through gaps in Ukraine’s air defenses, devastating its power infrastructure and casting Ukrainian cities into blackouts.