There are still some remaining concrete pillboxes and brick built blockhouses. "Johnston" shelled an observation tower and several blockhouses, pillboxes, and dugouts along the beach. The M20 proved useful against pillboxes and other types of field fortifications. The Japanese bunkers, actually log and earth pillboxes, proved resistant to artillery fire. The Arditi also used 37 mm and 65 mm cannons against pillboxes and fortifications. This network of bunkers, tunnels, and pillboxes favored the defense. The Japanese fought most of the battle from underground bunkers and pillboxes. Pillboxes, bunkers and other defensive works were built close to the ground. These flamethrowers were used to kill Japanese holed into pillboxes, buildings and caves. This network of bunkers and pillboxes favored the defense. The remaining eight were ad-hoc machine gun pillboxes, protected mostly by sandbags and earthworks. The OF-471 projectile was powerful enough against unprotected and entrenched infantry, pillboxes, and fortified buildings. His men honeycombed the island with more than of tunnels, 5,000 caves, and pillboxes. The ancient Royal Military Canal was well guarded with troops, pillboxes and barbed wire. Common targets included coastal defense guns, bridges, pillboxes, tanks, and shipping.