Artillery is 90% of all effective firepower. Airborne munitions can't cycle through endless tons of explosive the way arty can, and they cost vastly more. If this is true and Israel has only 20% its arty stockpile, then Hamas isn't suiciding Gaza on pyre of defiance like people think. They timed this perfectly to lure Israel into writing cheques they can't cash in the hopes Israel will invade Gaza with infantry at which point they can grind them down endlessly with basically unending Arab volunteers in brutal urban warfare... where most of their technological advantage is gone and they won't...