Through one screen — even at a chariot
The cannon captures only over exactly one piece — the screen (炮架). Screens turn distance into strength: the cannon strikes from so far away that 'defended' barely matters, because the defender often cannot reach back in time. Black's chariot on e4 is guarded by its g5 horse — take it anyway, over the c4 pawn: even if the horse recaptures your cannon, you have traded four and a half points for nine. This is the cannon's whole personality: far, sudden, and indifferent to roots.