Wizards have developed a Grasp-at-a Distance spell. It has numerous uses in everyday life of course but the Emperor (may he live forever) wants it to be deployed as a weapon of war.

Spell operation

1. A wizard (but no-one else) can grasp objects at a distance. Both hands (and other body-parts) can be used, as in normal life. Whatever body-part is used, full skin contact is required, so no gloves, etc.
2. Suppose my ale is across the room - I can reach out my hand and make a grasping motion. If I am accurate enough, it feels to me precisely as though I am holding the glass in my hand.
3. If I maintain the grasp and lift the glass, an observer will see it floating in exact synchrony with my hand - apparently in mid air.

Limitations

(a) If I pull the grasped object towards me, it will only move as my arm moves. In other words I can't pull it all the way. I have to bring it in arm-length stages. The simplest way is to alternate hands. It looks rather as though I am hauling on a rope. Eventually the object will be near enough to actually grasp it normally.

(b) I can't 'grasp' a red-hot or sharp object without injuring myself. The effect is exactly as though I was really touching it.

(c) I only have my normal strength so I can't 'grasp' and lift a weight that I wouldn't normally be able to lift. Most wizards are not at all muscly and non-wizards (e.g. warriors) cannot use the spell.

(d) I can break a fragile item precisely the way I could if I was holding it normally - the object will interact with items close to itself. My hand will interact with items close to me and objects near the object. .

(e) In most cases the wizard must be able to see the object being grasped in order to correctly and accurately locate it - this is the most difficult skill to master because your distant 'hand' is invisible. In theory someone who can play piano blindfold could play it at a considerable distance by first locating the piano and then finding the correct keys by touch even if they were too far away to be discerned individually.

(f) If the wizard grasps at a distance and someone else grasps the object normally, they won't feel each other's hands but will experience the forces. Thus a weedy wizard couldn't wrestle a sword away from a strong warrior who was holding the weapon firmly but the opposite would be the case.

Question

Non-fatal tests have been performed with the Emperor's own soldiers who weren't pre-warned. They soon learned to keep a tight hold on their weapons or strap them into their scabbards when not in use. They also learned to keep an eye on any obvious hand-movements by the wizards.

So - How can weedy wizards use their Grasp-at-a-Distance spell as an effective long-term weapon against powerful warriors?

Note

There are hundreds of warriors on each side in this battle but only ten wizards on the Emperor's side. They all know the spell. The other side has no wizards but a slight advantage in foot-soldier numbers.

Edits in response to comments

(1) No change in leverage. Just make sure you are standing on a firm surface and the area around you is clear. (2) No penalty for distance. In theory you could grope around blindly behind objects such as castle walls. However mind you don't accidentally grab something dangerous. (3) Eye contact is only needed to locate the object and that is the main problem. Trying to grasp a small object at a mile away could be tricky. That's why I mentioned the piano. It's easier to grasp the piano first and then slide your hand until you find the keys.