China is fueling Moscow’s war in Ukraine by sending fighter-jet components, navigational systems for military helicopters, and other technology since last year’s invasion, Russian customs data shows. The shipments, which are not weapons but have wartime uses, are reportedly among thousands of Chinese imports from both state-owned and private businesses recorded by the Russian customs office, a list that also includes telescoping antennas for military vehicles that can be used for communications jamming and parts for a radar system used to detect jets and missiles. Customs data compiled by the Washington-based national security nonprofit C4ADS and examined by the Wall...