OKINAWA - THE SHURI LINE
May 10th - 22nd, 1945

"You cannot by-pass a Jap because a Jap does not know when he is by-passed" A Colonel of the 96th US Infantry Division Two weeks after the campaign on Iwo Jima was officially over Operation Iceberg, the invasion of Okinawa, began. The decision to take Okinawa was made at the same time as that for Iwo Jima, and for much the same reasons.
The Americans thought they knew what to expect after the Iwo Jima campaign. A fanatical defence of position after position, each having to be winkled out by flamethrowers, demolition charges, and sometimes even direct fire from 14" naval guns. There were known to be around 100,000 defenders on the island, good quality troops in the main, well supplied with artillery and automatic weapons. The Japanese planned to defend the southern third of the island as they had the northern part of Iwo Jima - tunnels, caves, concrete emplacements and a strict ban on vain suicide attacks. This part of the island contained the best defensive terrain, as well as four air-bases, the port of Naha, and the best beaches and anchorages. The rest of the island would be covered by delaying forces, and left to the acknowledged US superiority in air and sea power. The defenders included the crack and experienced 62nd Division, the green 24th Division and the 44th Mixed Brigade, as well as numerous independent small units, including 10,000 naval troops, the elite 5th Artillery Command, the 27th Tank regiment and 20,000 native Okinawans (Boetai ). The Americans hit the island with everything they had. Carrier planes and B29s bombed airfields in Formosa, Japan and other nearby islands to suppress Japanese raids and kamikaze missions; a full week was spent pounding the island from sea and air. The invasion force consisted of the 7th, 27th, 77th and 96th Infantry Divisions, and the 1st, 2nd and 6th Marine Divisions, accompanied by 1,500 ships of all types.
The landings began on April 1st and initially went well. The Japanese had chosen not to contest the beaches. The 1st Marines landed and were held in place to act as the local reserve. The 6th Marines were given the task of clearing the north of the island, as they were not as experienced as the other Marine divisions. The 2nd Marine Division performed a landing feint near the south eastern corner of the island to pin Japanese reserves.
On the 6th of April the gigantic battleship Yamato, the pride of the IJN, sailed on a one-way mission to interdict the US Navy off Okinawa. The Allied air forces had kept an eye on her, and detected the movement straightaway. Within 24 hours, she joined her cousins on the sea bottom. But she had done some good: the distraction allowed a huge aerial kamikaze attack to achieve unprecedented success. An air armada of 700 planes, over half kamikazes, struck the US fleet. Six ships were sunk and seventeen damaged. If this rate of success was continued, the kamikazes had a real chance of delaying or even stopping the Allies at Okinawa.
It took until April 8th for the two Army divisions to work their way through the scattered defenders and outposts up to
the main Japanese defensive line along Kakazu ridge, one of a series of rugged terrain features that ran directly across the US line of advance. These defences were part of the first Shuri defence ring, a fortified line extending across the island through the town of Shuri, which was an ancient castle and the centre of the defences.
By April 12th, the defenders had brought the Americans to a standstill. The men would work their way up a hill through artillery, mortar and machine-gun fire, take the crest, and then be pinned down or driven back by the main Japanese position on the reverse face of the slope, almost immune from indirect fire. The 'blowtorch and corkscrew' tactics developed by the Americans, referring to the use of flamethrowers followed by demolition charges, were needed at almost every step. Often the defenders of a position were entombed alive and by-passed, only to appear elsewhere having escaped through a tunnel.
The Japanese command was divided between the cautious realists, led by the highly competent General Ushijima, and the 'fire-eaters', the junior and less experienced officers. Encouraged by the course of the battle thus far, Ushijima gave the fire-eaters their way on April 12th, and put in a six battalion attack that night. The Americans had decoded the signal flares using a captured signal book, and were prepared. By the light of star shells from the ships off-shore, US firepower blew the attack apart before it could get going. Still the Japanese persisted until the 14th, when Ushijima finally put an end to the slaughter. It was a return to the worst of Japanese tactics, relieved only by the lack of the suicidal and unproductive banzai charges. Lt. General Buckner, Tenth Army commander, decided on a large frontal attack to crack the tenacious defensive line. On April 19th all three front line divisions ( XXIV Corps) went over to the offensive.
The preliminary bombardment was ferocious. Over 600 planes, 18 warships and 300 guns opened up. The net result was estimated later to be about 200 Japanese dead. The defenders reappeared from their tunnels when the barrage stopped, and halted the advance in its tracks. The longest gain was around one kilometre in the west; many units ended the day on their start lines.
The 2nd Marine Division was again used for a landing feint to distract the defenders, who were in fact expecting another landing. In one of the most unfortunate decisions of the campaign, the experienced 2nd Marines were then sent back to Saipan, not having seen action on Okinawa at all.But the strain told on the defenders. Every gun, man or position lost could never be replaced. Slowly the Japanese were forced back by the unrelenting pressure. On the night of April 23rd/24th, the Japanese fell back to their second line. After a month of combat, the US Tenth Army was in trouble. Three infantry divisions, the 7th, 27th and 96th, had attacked for all they were worth against the first Japanese defensive line for three weeks and had taken more casualties than metres of ground.
There were two alternatives available to Buckner at this point: he could use his reserves (1st and 6th Marine and 77th Infantry Divisions) to replace his exhausted front line units, or he could make another landing behind the Japanese defensive lines.
Buckner chose the first course for two main reasons: he was in a hurry, and organising another invasion would mean two weeks of delay; and he feared "another Anzio, but worse". The 27th and 96th Divisions were pulled out on the April 30th and replaced by the 1st Marine and 77th Divisions respectively. The 7th had to wait another 10 days until the 96th was ready to return.
At first the fresh troops made little difference. For a week, the US troops advanced perhaps two kilometres in the centre, and less on the flanks. The Americans had run into the second Shuri line of the defence ring. The men had to go through it all again; the names changed but the tactics remained the same.
Ushijima once more allowed himself to be talked into an offensive. Encouraged by the stalemate at the front, he planned an attack for May 4th, to be accompanied by massive kamikaze strikes on the US Navy. The 24th Division, the 27th Tank regiment and the 44th Mixed Brigade were to lead the assault, and miscellaneous small units would make landings behind the American front to disrupt supplies and communications.
After a half-hour barrage of over 13,000 rounds, the attack went in early in the morning. The coastal landings were an abysmal failure; most were penned in or destroyed within minutes of debarking. The main assault met the fate of the earlier attack: US firepower rapidly decided the issue. Incredibly, another assault was put in the next night, and actually achieved a small breakthrough. By the next day, the Americans had restored the front and killed all of the successful attackers. The two attacks had cost the Japanese hundreds of planes, 5,000 casualties, almost all their tanks, and 60 precious guns. The US losses amounted to six ships sunk, six damaged, and 720 land casualties. The Japanese attack was another expensive failure. By May 11th the refreshed 96th Division was brought back into the line to replace the 7th, and the 6th Marine Division was added to the western flank. Buckner scheduled an all-out attack along the whole line for that day. The Japanese, certain by now that no second landing was coming, committed most of their reserves. The fighting went on, hardly moving, for ten days.
At the end of this period, the Japanese line was in danger. Both flanks were bending back, and the Americans were on the outskirts of Shuri in the centre. On the east coast, there was a real possibility of a breakthrough as the US troops opened a gap between the Japanese and the shoreline. At this point the rains, unseasonably late, started. Much of the front became a sea of mud, even stopping am-tracks. The only significant advance was made in the west, where the Marines finally took the town of Naha, largest in Okinawa but virtually deserted now.
The Marines also began to outflank Shuri to the south west. The situation looked desperate to General Ushijima, as he had no hope of reinforcement. The only viable option open to him was to abandon the hard-fought-for Shuri line and retreat into the very southern portion of the island, where a last defensive line had been prepared. The Japanese took advantage of the cover afforded by the constant rain to stage their withdrawal, skilfully covered by a rear guard. The withdrawal was complete by May 28th, but the Americans only realised that it had happened at all on the 30th, when a Marine unit slipped through a gap in the rear guard and took Shuri castle. Even then, the town proper held out for another day. When the men finally entered the ruined town, it was deserted.

"It's all over now but cleaning up pockets of resistance. This doesn't mean there won't be stiff fighting but the Japs won't be able to organise another line" General Buckner, May 31st 1945 By early June, when the rains had subsided, the Americans
were advancing faster than ever before. They had come three kilometres in a week - fast by Okinawan standards. They
started to by-pass the Oroku peninsula on the west coast, held by the troops of Admiral Ota's naval base force. On
June 3rd, two regiments of the 6th Marine made a landing on the northern point of the peninsula. The landing by sea was
considered easier than moving the men in the mud. The remainder of the Japanese forces on the island, about 30,000, had retreated to a new line in the south. Only one third of these, however, were trained infantry. The Japanese were running out of men. The support troops fought as bravely as the rest, but not so well. The now-familiar process of prising the defenders out of every nook and cranny in the convoluted hills continued. Tanks were of little use, as the ground was still soft from the rains. Again the Marines and the GIs faced the daunting prospect of resolutely held ridge lines raining mortar and machine-gun fire on them as they struggled up the slopes. The Japanese had very few heavy guns left, which eased the Americans' task somewhat. General Ushijima sensed the end was at hand, as the first ridge line fell in only 12 days. On June 17th, the Japanese front collapsed, so Ushijima, after one final, futile counter-attack, ordered his men to infiltrate through the US lines and carry on guerilla warfare in northern Okinawa. He and his staff took refuge in a cave near the island's southern shore. He committed hara-kiri on June 22nd, when US troops approached.
General Buckner was killed on June 18th by an artillery shell, in the final days of the drama that was Okinawa. He was the highest ranking American officer to be killed in combat in WWII, and he died only two months before the end. The total Allied losses were 49,000 casualties, of which 9,700 were naval personnel - the worst losses in the navy's history. The naval dead (4,900) outnumbered those of any other service in the campaign. They also lost 221 tanks (over half the original force), 36 ships sunk and 368 damaged, and 763 planes.
The Japanese losses were 110,000 troops and thousands of civilians. They also lost 16 ships sunk and 4 damaged, and, incredibly, 7,800 planes. But they had served their emperor well, and delayed the Allies by 83 days - nearly three times as long as originally estimated by the Allied planners. The island fighting had shown that the only way to deal with determined defenders who would not surrender was with fighting men of equal skill and determination who would not relent.
The desperate, resolute and intelligent defence of Okinawa by the Japanese must have been a factor in the decision to drop the atomic bombs on Japan. After all, if they fought in that fashion for an island populated by people they considered their inferiors, how would they fight for their homeland?