Plastic 6mm infantry can be fixed with solvent/plastic-weld quite well.
Metal 6mm infantry... Snap a few pix, send them to the store/person you bought them from, and politely ask for replacements. You can glue them, but chances are good you'll be repairing them repeatedly.

Then again, if you can find a use for them "off" the base, like Billchuck's idea above, or perhaps mounted on a vehicle, or even as "life-size" statues on a shrine or such, they can still be useful.