Okinawa: The Final Great Battle of World War II
The Battle of Okinawa started on 23 March 1945 with all major combat operations ending on 23 June 1945. The island of Okinawa is located approximately 350 miles south of mainland Japan. It is the largest island in the Ryukyu Island chain, the southernmost prefecture of the then-Japanese Empire. The strategic importance of this island cannot be overemphasized. In a time when an invasion of mainland Japan was necessary to end the war, Okinawa was an essential preparation ground and jumping-off point for the impending invasion. The island’s airfields were indispensable to the launching of bombers and long-range escorts for the preparatory bombing for the land invasion of mainland Japan. This battle involved the Japanese Army, minimal Japanese naval efforts (due to a lacking naval power), and the last of its airpower concentrated in mass kamikaze formations. The allied power consisted of a combined force that was largely American with some British naval support, along with the Joint Services of the U.S. Army, Marine Corps, and Navy.
The Pacific campaign started 7 December 1941 after the Japanese surprise attack on Pearl Harbor. The campaign crossed all over the Pacific. The Japanese initially had the upper hand in the air and on sea and land. After almost 4 years of naval, air, and land battles the tide had turned and by March 1945 the campaign had nearly reached its culminating point with American domination of the sea and air. It was now just Japanese territory that needed to be seized before the Japanese would admit defeat. The challenge faced by the American military was the Japanese willingness to fight to the bitter end, and that the island of Okinawa had been turned into a death trap for the American invasion force in order to display Japanese enthusiasm for the defense of its home territory. The American invasion force was led on the naval side by ADM Raymond Spruance of the 5th Fleet; the land assault force consisted of LTG Simon Bolivar Buckner’s 10th Army; the command of this invasion force was divided between MG John R. Hodge and MajGen Roy S. Geiger. The American forces were more than adequate to bring the island under Allied control. Fortunately for the Allies, there were no additional adversaries or a significant naval presence to threaten the invasion force that were not organic to the Japanese defense force; the Japanese had no allies in the region and the Nazi regime would fully collapse halfway through the battle leaving Japan to stand alone against the Allies. The Japanese garrison on Okinawa was led by GEN Mitsuru Ushijima with a force of nearly 130,000 men (from his 32d Army) in addition to a 20,000-man home guard to supplement his forces. The defense force was battle hardened, well prepared, and willing to fight to the death but they could not contend with the professional capability of battle hardened American troops who were supplemented by the almost limitless newly trained troops. The path to the Battle of Okinawa arose from a long and bloody path to get closer to the mainland of Japan and was the final stepping stone to an invasion.
Map 1. The Pacific theater.1
Okinawa is a subtropical island that stays hot and muggy year round with almost continual precipitation. The precipitation did not have an effect on either side’s weapons or equipment due to experience in maintaining the weapons and gear in such conditions. The effect of the precipitation on morale was dramatic for the American troops. In addition, the physical effects increased disease while decreasing operational efficiency by increasing the prevalence of mud preventing any sort of mechanized support. The terrain on Okinawa was covered in foliage and trees and was littered with hills, one of which reaches 505 meters at its highest point. The combination of these factors gave the advantage to the defender on this long island. The Japanese also used the coral and limestone as natural cover and concealment. The Japanese were able to create defensive lines that took away any good avenue of approach from the attacker by occupying every ridgeline on the southern portion of the island. The Japanese took advantage of all the island’s natural obstacles and enhanced them through the utilization of tunnels and fortified defensive positions. The dense foliage and well-constructed defensive positions (particularly in the southern end of the island) provided as advantageous cover and concealment as a defender could ask for.
Map 2. Terrain map of the island of Okinawa. The notable features of the island are the scattered hills which allowed the Japanese to create defensive lines at each ridge forcing a bloody fight for every inch taken.2
The strength and composition of the American landing force consisted of LTG Buckner’s 10th Army of some 180,000 men. The 10th Army included MajGen Geiger’s III Marine Amphibious Corps (1st, 2d, and 6th Divisions) and MG Hodge’s XXIV Army Corps (7th, 27th, 77th, and 96th Divisions). Moreover, the naval support consisted of more than 40 aircraft carriers and 18 battle ships (more than 14,000 ships in total) plus British support in addition to other landing craft and ships. The Japanese defenders’ land composition (the naval support was not even a factor) was formed into the 32d Army (Ryukyu Island chain defense force) comprised of four divisions (9th, 24th, 28th, and 62d on Sakishima) plus additional home guard units. The advantage in this battle was absolutely on the side of the Americans due to endless resources available to them in addition to a vast technological advantage in nearly all aspects. The American naval and air power was not only superior in numbers as the Japanese Zeros were no match for the more advanced American fighters and antiaircraft guns manned by experienced gunners on the American ships. Even with the addition of the Okha, a Japanese rocket-powered suicide missile launched from a bomber with a 2,650 pound warhead and formidable once released, the Americans quickly learned to shoot down the bombers prior to the Okha being released. Still the mass formations took their toll on the 5th Fleet starting on 6 April, sinking or badly damaging an average of one and a half ships per day. The land battle also gave the advantage to the Americans given their engineer, mechanized, medical, and all other kinds of logistical support, thereby sustaining the fighting power and longevity to the Americans. Additionally, technologically nearly all of the American equipment was superior and far more reliable; this included weapons ranging from small arms to howitzers and all the way to the 14-inch guns on the battleships.
At this point in the war both the Americans and the Japanese had developed their command, control, and communications in ground warfare to the best level of efficiency they could. The Japanese were far more rudimentary with a simple, straightforward concept—to kill every single American fighter possible and hold the defensive line until it was utterly broken. This concept of defending, delaying, and withdrawing to another defensive line was a change in tactics for the Japanese. Typically the Japanese Army mounted a Banzai run once the defensive line could no longer hold, always resulting in large numbers of Japanese soldiers being torn apart by American machineguns, mortars, rifles, and an assortment of small arms. This tactical change was the brainchild of GEN Ushijima whose intent was to have his men live and hold out as long as possible in an effort to slow the American advance toward Japan. The decision as to when to withdraw to the next defensive line was made ultimately by GEN Ushijima, who received reports from his many officers along whichever one of the three defensive lines was being held at the time. GEN Ushijima held each line until its fate was sealed but there was still opportunity to tactically withdraw, set up in the defense, and start the process all over again. The elaborate communications network under the Shuri Castle where GEN Ushijima’s headquarters was located allowed him to make informed decisions as the castle was a highly defensible position at the center point of the middle Shuri defensive line. The naval contributions of the Japanese, which were almost nonexistent, were best exemplified by the Japanese Navy’s own suicide run from their final massive 70,000 ton battleship Yamato being destroyed when it was spotted on its way to Okinawa. The Yamato was loaded up with just enough fuel to get to the American fleet and ordered to fight to the death; its strategy was to beach itself near the Shuri line and decimate American troops already pinned down by the 100,000-strong defenders of the Shuri line while also taking advantage of any opportunity to sink American ships. Japanese air power was no longer intent on defeating the Americans in head-to-head battle but was instead depending upon its kamikazes. At this battle the first mass formations of kamikazes were utilized against the 5th Fleet.
The American command, control, and communications were as efficient as they could be by 1945 after nearly 4 years of battling in the Pacific. The advancement of communications processes and independence within small units created a new level of efficiency on the battlefield. There were still command-level issues in appropriate decisionmaking but the majority of them were eliminated as all the commanders were already battle hardened; in addition, the small unit leaders largely made up for command and control failures by improvising and adapting to every obstacle. Units had developed a cohesive esprit de corps throughout all of the units in the American Services.
The prebattle intelligence gathering for the Americans was sparse in attaining valuable collections because of the isolation of the Ryukyu Island chain. There was limited intelligence gathered from old Japanese newspapers as well as from Japanese prisoners of war from other battles in the Pacific. Aerial photographs did not yield an accurate picture of the Japanese defensive strategy. The aerial reconnaissance was hampered by continual cloud cover over the majority of the island. The clever concealment of the Shuri line, in addition to most of it being underground, prevented its elaborate nature from being discovered. Intelligence was clearly lacking given the presumption that 80 to 85 percent casualties were expected on the beachhead, when in reality there was almost no resistance. Intelligence was also unaware of the buildup of the 32d Army by Japanese troops from Burma. The Americans knew there would be a heavy defense force but the overall strength and where they came from was a mystery. Useful intelligence gathering and dissemination did not begin until contact with the Shuri line began. It was then that awareness of GEN Ushijima’s plan for a war of attrition began to develop and the intricate nature of the Japanese defensive lines discovered.
Figure 1. Picture of the torturous terrain that had to be taken by the Americans.3
The tactical doctrine of the American troops was well ingrained by this point in the war. The majority of both the Army and Marine Corps were experienced combat veterans and were well accustomed to Japanese warfighting tactics. The troops on Okinawa had already become experts in utilizing their combined arms assets in driving out the Japanese. The employment of mortars, grenades, satchel charges, other forms of explosives, and flamethrowers was commonplace and necessary to force the Japanese out of fighting positions. Though the American tactical employment was well indoctrinated there was an unexpected variable that the Americans faced: the evolution of the defensive tactics adopted by the GEN Ushijima’s forces. Typically the Japanese emphasized the importance of dying for the Emperor, but Ushijima put an additional responsibility on his men expanding beyond that. Ushijima had concentrated the bulk of his defenders out of range of Allied naval guns off the beaches and behind the strong Shuri line at the southern end of the island, postulating that holding out as long as possible was the most honorable and beneficial death to give for the Emperor. He wanted to slow the American advance as much as possible to allow the mainland Japanese force to shore up its defenses and prepare its people for a bloody battle all across Japan. Therefore Ushijima adopted a tactic of attrition, holding out as long as possible, taking advantage of the terrain, and showing the Americans how costly it would be to continue the campaign through a price paid in American lives.
The minds of the American troops were tense and morale was low preceding the invasion as the estimates of casualties were very high—80 to 85 percent on the initial amphibious landing. The first week of the battle turned out to be more calming than the week leading up to the landing (largely due to the shelling the Marines and soldiers had to live with on the ships) and for the Marines in the north of the island, the slow tempo maintained for almost 3 weeks as the defenses in the north of the island were very light. This helped to increase the morale for a short period but the torrential rains throughout the battle and the impact of the Shuri line defenses quickly took their toll. More mental health issues arose from the Battle of Okinawa than any other battle in the Pacific during World War II. The constant bombardment from artillery and mortars coupled with the high casualty rates led to a great deal of men coming down with combat fatigue. Additionally the rains caused mud that prevented tanks from moving and tracks from pulling out the dead, forcing Marines (who pride themselves on burying their dead in a proper and honorable manner) to leave their comrades where they lay. This, coupled with thousands of bodies both friend and foe littering the entire island, created a scent you could nearly taste. Morale was dangerously low by the month of May and the state of discipline on a moral basis had a new low barometer for acceptable behavior. The ruthless atrocities by the Japanese throughout the war had already brought on an altered behavior (deemed so by traditional standards) by many Americans resulting in the desecration of Japanese remains, but the Japanese tactic of using the Okinawan people as human shields brought about a new aspect of terror and torment to the psychological capacity of the Americans.
The Japanese Army on Okinawa was pulled largely from Burma. They were well trained and experienced troops with leaders who were fit to fight and both tactically and technically proficient in their profession. A drawback for the Japanese leaders was not having a large amount of latitude in their command; they lacked the authority to choose when and how to employ their units which hamstrung the Japanese throughout the war. This, however, did not restrict the Japanese from being successful in their southern Okinawa defenses as the concept was to employ their combined arms and overlapping fields of fire to tear apart the Americans. The planning for the defensive strategy was incredibly elaborate and the Japanese commanders knew it down to the smallest detail. The small unit leadership of the Japanese was effective in employing the tactics in which they had been trained; however, taking initiative and adapting to the situation had not been part of their repertoire, thus giving the leadership advantage to the Americans.
The American leadership within all Services, from the lowest private through GEN Buckner and ADM Spruance, was of the most superb capability, proficient in all regards of their military profession. This strength of leadership was evident from the basic rifleman to the logistician to the tactician. The small unit leadership was exemplified in its superior performance and capability by the 24 Medals of Honor awarded for heroism during the Battle of Okinawa. The leadership in this battle was less dependent on tactical maneuvering and operational planning on a large scale and far more about small unit leaders facing utter chaos and destruction, leading from the front, and continuing to press on through hammering fire and mounting casualties. The objectives of the attacking Americans were relatively simple and always consisted of “take a hill and hold it.” This was consistent with the operational goals of taking the entire island but first each defensive line had to be eliminated. This was done with precision force focusing on specific objectives but still having to fight inch by inch, taking the hills that anchored the edges of the defensive lines, forcing the Japanese to withdraw.
The bombardment of Okinawa commenced on 23 March and lasted until the morning of the land invasion (codenamed Operation Iceberg) on 1 April. The objectives were split between the Army and Marine Corps divisions. The MarDivs would take the northern three-quarters of the island while the Army divisions would take the more strategically significant southern quarter that held the island’s capital and the majority of the airfields. The landing on 1 April (Easter Sunday and April Fools’ Day) went almost completely unopposed as did the next several days. There was minimal resistance for the Marines who completed taking their objectives to the north on 20 April. The Marines faced only sporadic resistance during this period and spent most of their time and effort easing the concerns of the Okinawan citizens who were indoctrinated into the belief that the Americans would torture and murder them. Once the Marines had accomplished their mission, they moved south to assist the Army troops. By the morning of 6 April the Army had met the outer defensive Shuri line where the Japanese opened up on the Army troops with overwhelming fire power. By 24 April the outer defensive ring of the Shuri line had been taken after 18 days of hard fighting but this was the softest of the three defensive lines as the Americans would soon discover. As the first defensive ring was eliminated, the Japanese troops simply withdrew to the second defensive line which was the most heavily fortified and intricate. This line utilized every natural and manmade advantage that it could, incorporating them into an ingenious defensive strategy. The limestone and coral landscape was used as natural cover while every single weapon employed was mutually supported by other combined arms assets. Every ridge was honeycombed with defensive positions allowing the Japanese to always hold the high ground and employ relatively small numbers of infantryman, machinegunners, and mortarmen against a numerically far-superior adversary who had to move through ravines, across rivers, and up hills resulting in a dramatic advantage for the Japanese. However, the Americans did manage success against the Japanese defensive lines which prompted GEN Ushijima to go on the offensive.
The Japanese major counteroffensive on 4 and 5 May was a dramatic failure resulting in more than 3,000 casualties and no ground gained. Though carefully planned, the Japanese did not acquire accurate intelligence identifying weak spots in the defensive line or locations of American command posts. This, coupled with inexperience in diverse types of offensive maneuvers outside of Banzai attacks (the Japanese attempted to assault multiple objectives in addition to an amphibious assault), led to the slaughter of Japanese soldiers, expediting the breaking of the Shuri line. As noted by a Marine, the environment that was lived and fought in was so atrocious, words could not accurately describe it. It required all of the senses to truly understand the horrors of the battle. There were piles of dead bodies at the bottom of every hill and if someone was to slip in the mud and fall down a hill, they were apt to reach the bottom vomiting. Said one Marine of the scene, “I saw more than one man lose his footing and slip and slide all the way to the bottom only to stand up horror-stricken as he watched in disbelief while fat maggots tumbled out of his muddy dungaree pockets, cartridge belt, legging lacings, and the like.”4
Map 3. Japanese-planned counteroffensive.5
The key to taking the second Shuri line was taking the anchoring positions on the west end at Sugar Loaf Hill (the Marines took Sugar Loaf and the other two hills creating a horseshoe held by the Japanese) and on the east at Conical Hill (which the Army took). The complex of Sugar Loaf Hill, Horseshoe Ridge, and Half Moon Hill was one of the most fiercely contested regions in the entire battle. With each hill covering the other two, the Japanese had connected the three hills with hidden galleries and set up interlocking fields of fire by machine gun and various types of artillery.6 It took a week of back-and-forth fighting on Sugar Loaf Hill (and the other two hills that were next to it that created a death trap for troops moving up any of the three hills) with the Marines taking the summit more than 10 times. However, the casualties resulting from the attack and the subsequent counterattacks by the Japanese led to ownership of the hill changing many times with the Marines fully occupying and finally owning it on 18 May.
Map 4. The last push for Sugar Loaf Hill by the 6th Marine Division.7
Map 5. Typical defensive infrastructure of an Okinawan hill.8
By 22 May the main Shuri line had been seemingly beaten and the Japanese began their withdrawal of the majority of its remaining 30,000 troops to the final defensive line on the southern tip of Okinawa. The defeat of this line forced GEN Ushijima to withdraw from his command post located more than 150 feet underneath the Shuri Castle (which was still protected by a Japanese rearguard whose purpose was to slow the American advance while the new defensive line was prepared). The heavily fortified command post bunker required eviction through the use of significant amounts of high explosives and flame throwers in order to expel the Japanese from their hiding places or killing them in place. The most gruesome method applied was to pour scalding hot oil down the elaborate tunnel system. The Marines were successful in breaking the Shuri line through intelligent preparation and utilizing clever offensive tactics prompted by the command.
MajGen Lemuel C. Shepherd, Jr., Commander of the 6th MarDiv, had warned his troops that the battle in southern Okinawa would be different from anything they had previously encountered in the Pacific. In a training order read twice by every platoon leader to his men, MajGen Shepherd described the enemy’s intelligent use of artillery, his ample supplies, his defensive line “which cannot be breached by simple frontal attack without heavy losses,” and his willingness to counterattack by every available means. MajGen Shepherd urged his commanders and troops to take advantage of cover and camouflage, to use maneuver in outflanking the Japanese rather than to try to “outslug” them, and to keep driving. “Your enemy can’t think as fast as you can and he is no match for a determined aggressive Marine who has confidence in himself and his weapon.”9
With the Japanese defense forces isolating themselves for their final defense on the southern tip of the island, the Marines made the final amphibious assault of the war cutting behind the Japanese lines and clearing out the Japanese defensive positions with grenades and flame throwers. During this push to the southern tip of the island, the Marines and soldiers did what they could to tend to the Okinawan people. On 21 June the final contact for the Battle of Okinawa began. Instead of staying on the defensive, GEN Ushijima conducted one final offensive that, if successful, would have extended the battle further. Like most of the Japanese offensives on Okinawa, it was an utter failure. Though Ushijima made his troops aware of his respect for the honor they had given the Emperor by delaying the Americans for nearly 3 months, it was not enough. Ushijima wrote the following in a letter before committing ritual suicide on the 22 June:
To my great regret we are no longer able to continue the fight. For this failure I tender deepest apologies to the Emperor and the people of the homeland. We will make one final charge to kill as many of the enemy as possible. I pray for the souls of men killed in battle and for the prosperity of the Imperial Family.10
On 23 June all major combat operations ended on the island of Okinawa. Over the 3 month battle more than 8 million artillery and mortar rounds were fired, the equivalent of more than 1 round per second. For some, the silence after the battle was over was almost deafening. In total, more than 12,000 American servicemembers were killed and more than 38,000 wounded (many from combat fatigue) or missing. The Japanese military lost more than 110,000, but the greatest loss of life by the Okinawan people. Anywhere from 40,000 to 150,000 of the Okinawans perished during the battle. Even with all the carnage, it was at Okinawa that the largest number of Japanese soldiers were taken prisoner (more than 7,000—an unprecedented number).
Map 6. American troop movement during the Battle of Okinawa.11
The Battle of Okinawa had a dramatic effect not only on the Pacific campaign but on the nature of warfare to this day. The battles in the Pacific made evident to America that they could defeat the Japanese in any fight. The painful realization from information gained from Okinawa was the high price that would be paid for every inch of Japanese land the Americans took. The Japanese mainland defense force was more than 1 million strong. In addition, the Japanese possessed 8,000 aircraft and kamikaze pilots who were being trained every day. Even the civilian population was trained for combat with the invading Americans; suicide attacks by civilians were expected. The greatest effect Okinawa had on the Pacific campaign was to convince the recently seated President Harry S. Truman to take any avenue to end the war outside of sending an invasion force onto mainland Japan as, unfortunately, firebombing the country was not adequate to convince the Japanese to surrender. The concept of conceding was one the Japanese simply could not fathom; admitting defeat without being completely subdued by their adversary was unconscionable to the Japanese. This was all too apparent to President Truman who said, “I do not want another Okinawa from one end of Japan to the other.”12 This sentiment is what lead to the approval of the atomic bomb Little Boy being dropped on Hiroshima on 6 August. Even with the resulting vast destruction, the Japanese were still not willing to concede. The war cabinet was divided even after Fat Man was dropped at Nagasaki on 9 August. It still took negotiating to determine the status of Japan’s surrender which unofficially took place on 14 August with a compromise that Emperor Hirohito could maintain his seat as emperor so long as he followed the orders and directions of the Supreme Allied Commander. This was carried out by GEN Douglas MacArthur who ostensibly ran Japan for the next 6 years after receiving the Japanese formal surrender from the Japanese Foreign Minister Mamoru Shigemitsu on the USS Missouri (BB 63) on 2 September 1945.
1. Image from the National Archives, World at War: Understanding Conflict and Society, s.v. “World War II: Pacific Theater,” accessed 15 April 2012 at http://worldatwar2.abc-clio.com.ezproxy1.apus.edu/.
2. Appleman, Roy E., “United States Army in World War II: The War in the Pacific,” HyperWar, last modified 2012, accessed 9 April 2012 at http://www.ibiblio.org/hyperwar/USA/USA-P-Okinawa/maps/USA-P-Okinawa-4.jpg.
3. Stevens, John, “Illustration No.59,” HyperWar, last modified 2012, accessed 8 April 2012 at
4. Chen, Peter, “Mitsuru Ushijima,” Divine Wind, last modified 2012, accessed 6 April 2012 at http://ww2db.com/person_bio.php?person_id=306.
5. Stevens, “Map No.37,” last modified 2012, accessed 5 April 2012 at http://www.ibiblio.org/hyperwar/USA/USA-P-Okinawa/maps/USA-P-Okinawa-37.jpg.
7. Stevens, “Map No.43,” last modified 2012, accessed 1 April 2012 at http://www.ibiblio.org/hyperwar/USA/USA-P-Okinawa/maps/USA-P-Okinawa-43.jpg.
8. A typical defense system on the face of Iegusugu Pinnacle, Okinawa, Japan. Illustration from CINCPAC-CINCPOA Weekly Intelligence, Volume 2, Number 5, 13 August 1945, accessed at http://ww2db.com/image.php?image_id=6636.
11. “Okinawa, 1945,” World at War: Understanding Conflict and Society, accessed 17 April 2012 at http://worldatwar2.abc-clio.com.ezproxy1.apus.edu/.
12. Weintraub, Stanley, The Last Great Victory: The End of World War II, July/August 1945, Truman Tally Books/Dutton, New York, 1995, p. 57.