To make matters worse for the Americans , the bunkers were connected to the elaborate tunnel system .
Bunkers that were cleared with flamethrowers and grenades were reoccupied shortly afterwards by Japanese troops moving through the tunnels .
To make matters worse for the Americans , the bunkers were connected to the elaborate tunnel system so that bunkers that were cleared with flamethrowers and grenades were reoccupied shortly afterwards by Japanese troops moving through the tunnels .