I kept specifying "small, stealthy UAVs" - which by definition would
be used for recce, not attack - as these are the hardest targets to
detect and destroy. Now it may be that powerful navies will not be too
troubled by what they can do (you can't hide a ship too easily anyway,
so their enemy will know they are there) but armies certainly are
worried, because UAVs can be used to detect the movements of troops and
vehicles and identify targets for attack - even to lase them to guide
in homing munitions. And some of the recce UAVs being developed at the
moment are really small and quiet and will be very difficult to spot.

Even if SAMs could deal with these small UAVs, the problem would be
that the enemy could then just send over hordes of very cheap UAVs
(without the expensive sensor kit) to soak up the SAMs - a very
cost-effective way of degrading your enemy's capabilities. Unless and
until a small and cheap "anti-UAV" homing missile can be developed, I
think appropriate guns (and ammo) provide the best answer.

It is of course correct that a big, weapon-carrying UAV will be much
easier to detect than a small one (although a stealthy design may still
cause problems, just as stealth strike planes do). In contrast, fast
anti-ship missiles may be difficult to intercept but they have hot
engines and leading-edge surfaces which are easy to detect with IR
sensors: stealth and high speed do not go together very well.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk