For decades Russia has, more than any other country, aided China's dramatic military modernization with weapons and technology — and now Beijing has plenty that Moscow needs as its Ukraine invasion continues, military analysts say.

At the top end, China has developed systems, such as reconnaissance and armed drones, guided weapons and battlefield communications, that might help Russia fill gaps that are being exposed on the Ukraine front.

Russia might also need more common materiel, such as anti-tank weapons, trucks and ammunition, that China has in storage.