While General Buckner knew soon after the initial landings that the Japanese had concentrated their forces on southern Okinawa and had elected to fight the battle there, he did not then know the true extent of these defenses. The strength of the Shuri fortifications was first fully revealed in the heavy fighting between 8 and 23 April, when the Japanese positions held against furious American onslaughts. Across the entire front line evidence fast accumulated that the Japanese held tightly, from coast to coast, a dug-in, fortified defense line, reaching in depth as far as Yonabaru-Shuri-Naha. The failure of the American attack to break through the Shuri line led to a review of the tactical situation and of the tactics required to overcome Japanese resistance with the least possible cost and time.
As the Americans came up against the Shuri line veteran fighters in the Pacific noted many familiar tactics and techniques in the Japanese defense. Intricate and elaborate underground positions, expert handling of light mortars and machine guns, fierce local attacks, willingness of Japanese soldiers to destroy themselves when cornered, aggressive defense of reverse slopes, full exploitation of cover and concealment, ceaseless efforts to infiltrate the lines—all these were reminiscent of previous battles with the Japanese from Guadalcanal to Leyte.
The enemy had shown all his old ingenuity in preparing his positions underground. Many of the underground fortifications had numerous entrances connected by an intricate system of tunnels. In some of the larger hill masses his tunneling had given him great maneuverability where the heaviest bombs and shells could not reach him. Such underground mobility often enabled him to convert an apparent defensive operation into an offensive one by moving his troops through tunnels into different caves or pillboxes and sometimes into the rear of attacking forces. Most remarkable was the care he had lavished on positions housing only one or two weapons. In one place a 47-mm. antitank gun had a clear field of fire to the east from a pillbox embrasure set into the hill and constructed of heavy stone slabs and coral blocks faced with mortar; a tunnel braced with heavy timbers ran from this embrasure fifteen feet into the hill, where it met another tunnel running out to the north slope of the hill. A heavy machine-gun emplacement near Oyama consisted of two pillbox-type dugouts looking out to the north, strongly constructed and connected with the southwest slope of the hill by a long, unbraced tunnel cut through the coral and lime formation. A cave 400 yards north of Uchitomari, with an opening only 3 by 4 feet, led into a 70-foot tunnel that adjoined two large rooms and received ventilation through a vent extending 30 feet to the top of the ridge. Some pillboxes had sliding steel doors. Experienced officers described such positions as "both artful and fantastic."{307}
The most striking aspect of the enemy's resistance was his strength in artillery. Never had Pacific veterans seen Japanese artillery in any such quantity or encountered such effective use of it, especially in coordination with infantry attacks. Together with hundreds of mortars from 50 mm. to 320 mm. the enemy had quantities of light and medium artillery and dual purpose guns. He was strongest in 70-mm. and 75-mm. guns, 75-mm. and 150-mm. howitzers, and 5-inch coast defense guns. The 2d Battalion of the Japanese 1st Medium Artillery Regiment, located initially south of Kochi and Onaga, typified his artillery organization. It was composed of three batteries, each with four 150-mm. howitzers, the best Japanese weapons of that type, which could fire 80-pound projectiles at a maximum range of 11,000 yards. Each battery had four prime movers—6-ton, full-tracked vehicles that could be used for hauling ammunition as well as for towing the howitzers.{308}
Usually widely dispersed as defense against American bombing and shelling, the Japanese artillery was nevertheless closely integrated into the general tactical scheme of the Shuri defenses. The keynote of the enemy's defensive tactics around Shuri was mutual support through coordination of fire power. The enemy command indoctrinated the defenders of each position with the importance of protecting adjacent positions as well as their own. "It must be borne in mind that one's own fire power plays an important part in the defense of the neighboring positions and vice versa," a 44th Brigade order read. "If one's own fire power is not fully brought to bear, neighboring positions will be destroyed, and their supporting fire power lost against an advancing enemy, thus exposing oneself to danger."{309}
12-cm. British gun in concrete emplacement