Proliferation of cheap one-way drones was made possible by a complex global supply chain that keeps leading back to China. In early July, terrifying shrieks were heard across Kyiv as Russia launched Shahed drones powered by turbojet engines. The Shahed drones, now more like missiles, were capable of flying up to around 300 miles an hour, roughly three times as fast as older versions.

Some 30 people were killed in the attack, which also included ballistic and cruise missiles. Washington's main strategic rival has long served as arguably the most important clearinghouse for Shahed components, including engine parts, servomotors and gyroscopes, according to current and former U.S. officials and analysts. It is part of a complex global supply chain that analysts say enabled an isolated country—Iran—to pioneer and share one of the most transformative military innovations of the era: cheap, flying, killing machines that have bedeviled the U.S. and its allies, added to the civilian toll in Ukraine and undermined America's military edge in the Middle East.

China's foreign ministry didn't respond to a request for comment. It previously said it strictly regulates the export of "dual use" components, which can serve both civilian and military purposes. It rejects unilateral U.S. sanctions that punish unauthorized trading of such parts, saying they violate international law.

The Shahed—a deceptively simple and destructive flying wedge of fiberglass, microchips and explosives costing as little as $20,000—helps show how weapons proliferation has changed, and why tapping global supply chains is now so important. In the past, technological innovations in warfare tended to come from major powers that had their own industrial bases, enabling them to produce their weapons at scale. The AK-47 rifle is a good example: It was developed by Russian designers, influenced by a German assault rifle, then mass-produced by the Soviet Union's sprawling factories.

In today's world, however, any country with an idea for a weapon—even a middle power such as Iran—can turn to cheap parts suppliers abroad, especially in China. To develop Shaheds, Iran employed a design pioneered by the U.S. and West Germany. To actually make them, however, Tehran had to source parts from across the globe, including Western nations as well as China.

Yet even the Western parts tended to get moved through shell companies in mainland China or Hong Kong to disguise their origin, and over time, many were replaced by components made there, according to former U.S. officials, Ukrainian officials and analysts. Hong Kong's government said it vigorously enforces United Nations sanctions but not those imposed unilaterally by individual nations, which it says violate international law. The Shahed and its variants continue to wreak havoc.

Shahed drones helped devastate a U.S. base in Bahrain at the start of the war with Iran, fueling Navy logistics problems. Ukraine's air force says Russia has launched Shaheds each night this month. Such drones have also forced the U.S. and its allies to burn through pricey interceptors.

China and India have revealed their own versions. Iran has also sold its drone technology to Venezuela, Syria and Ethiopia, according to the U.S. Department of Defense, while Russia's Africa Corps has used Shaheds in Mali. The U.S. military, meanwhile, was inspired by Shahed technology to develop a low-cost drone that it has used in the war with Iran. "We're going to see these things everywhere," said Mick Ryan, a military analyst and retired Australian Army major general.