[GlibMonkeyDeath]

>What good are drones, except as weapons of assassination? Can't use them in an conventional war, there are shields.

Presumably a drone could get close enough to push a blade through the shield (maybe use a rocket booster or some other advanced "suspensor" tech) at low-ish speed (a knife would have to travel through the shield on the order of a human reaction time, otherwise even knives wouldn't work. That's about 0.1s/0.1 m, so 1 m/s - ish.)

[GeoAtreides]

if it moves slow enough to pass a shield, it moves slow enough to be easily dispatched. And remember, no autonomous behaviour, there has to be human operator. And it's very expensive. It just doesn't scale.

[GlibMonkeyDeath]

OK we are really nerding out here but I just can't resist :)

The propelled blade weapon doesn't need a control system in the "shape of a human mind" to be effective. A very simple control system would work. If they have ornithopters, then they have control systems. The blades could even work like hawk talons (so an ornithopter drone falling on a shielded fighter, then springing what is effectively a pointed metal trap.)

But more importantly, you are right that if the weapon moves too slowly, then you could just get out of the way. That's true of any weapon, no matter how it is propelled. That's why I said above you have to be able to penetrate a shield faster than a human reaction time, otherwise no weapon would be effective.