What I actually mean is for peaceful purposes. Would it be possible to activate huge magnets to disarm the opposing army or to 'catch' bullets, missiles, shells etc in a sort of magnetic force field so that they explode harmlessly away from people?
Bullets are made of lead which is non-magnetic, so that's one immediate problem.
Anything else with magnetic components could be rapidly redesigned using non-ferrous metals or plasic based composites. There is unfortunately an enormous amount of money to be made in the weapons industry where people are working to invent new and more efficient ways of killing other people, your idea would only be a minor inconvenienve to them.
A fast moving piece of metal in a magnetic feild will set up edy curent and a related feild, the two field would then itnereact - only a conductor is needed. Most weapong contain metal someware in them
This is not a practicable idea. Distance would soon diminish a magnetic field to an ineffective level.
Incidentally, this is no new idea! I experienced many air raids during WW2 and I remember that the suggestion was then forwarded that magnets be placed in surrounding fields to deflect the bombs. I believe the suggestion was never adopted!