Siege Stones

A game of abstract strategy. Players attempt placing pieces (either stones or towers) on the board. Stones threaten towers, controlling them. Whoever gains control of four towers, wins. Stones are also affected by towers. The more towers next to it, the less effective the stone. One well-placed tower may free two others. One carefully positioned stone could win the game. You have 20 stones each and 9 towers to vie for. Can you take the towers?