The trick was to get the chains on the dragon, everyone knew that, including the dragons. One loop around a foot was enough, then the words engraved on the chains could take effect. The dragon, desperately trying to get away, would dive and weave, holding its limbs close to its body so the flung chains wouldn’t catch. Sometimes the dragon would eat one or more of the hunters. Sometimes the dragon would die. Usually the hunt would end with the dragon being dragged across the ground back to town where proper command chains could be welded around it and it could be put to work.
Dragons hauled, dug and carried under the control of men. They did enormous amounts of work and you didn’t have to pay them. They really didn’t eat that much, given their size and the work they did. Some men grew rich on cheap dragon labour, and began to think that all their labour should be that cheap, so they went to the wizards who made the chains and got new chains made. Chains with smaller links and slightly different words…
Men started turning up in chains then, men with clever hands who turned the ores the dragons dug up into metals. Men with sad eyes whose chains compelled them to work as hard as dragons. Clever men who realised that dragon talons could scratch metal, even enchanted metal. Clever men who realised that the dragons had not been forbidden to damage the chains of the human slaves.
A few careful scratches and the human slaves were free of their orders. A few chisel strokes and they were free of their chains. A lot of chisel strokes and the dragons were free. Then the civilization of the dragon-takers died in flames of hot vengeance.
The mages that crafted the chains engraved with commands were dead and nothing that survived was strong enough to oppose the rise of the dragon borne and their partner mounts.