A jet engine on a drone buys speed over a propeller, and on a Ukrainian air-defence crew's screen speed is the one thing they cannot get back. On Sunday Ukrainian President Volodymyr Zelenskiy said he believed Russia may have shared jet-drone technology with North Korea, its longstanding ally. He said "believed" and "may have", and he is a man with a stake: every transfer that sends Russian know-how east is one more supplier for Moscow's war and one more customer for what Moscow knows.

Messages cost nothing. When China and Russia sent anniversary greetings to Kim Jong Un on 9 September, reaffirming strategic ties, no one's books moved. Jet-drone know-how, if it moved, was a delivery, and deliveries leave a counterpart in someone's books: drawings, engines, engineers, or, more precisely, whatever Pyongyang handed back, which Zelenskiy did not say and the reports do not supply.

The same weekend gives the claim its setting. North Korea said on Sunday it had tested a hypersonic missile under Kim's supervision, a drill aimed at demonstrating the reliability of its nuclear deterrent. Separately, an expert said North Korea's intermediate-range missile test puts Guam and parts of Alaska within range, as President Trump touts his relationship with Kim. The expert's account has Kim rebuffing Trump's outreach.

So the people who feel it first sit at two ends of one supply line. At one end is the Ukrainian crew who will have less time per drone if the claim holds. At the other are the planners on Guam and in Alaska, now on a range table that includes them.

Kyiv has made an accusation and offered a belief, not a document. Moscow's answer will likely be a denial or silence, and neither would name a ledger entry.