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Battle of Okinawa
April 1 – June 22, 1945· Battle· Asia & Pacific
Well documentedSolid records, physical evidence or scientific consensus.
The last major battle of the Pacific war: an 82-day US invasion of Okinawa, an island close to Japan's home islands.
See it on the Battles & Wars map →What happened
On April 1, 1945, US Army and Marine troops landed, backed by the largest naval force of the Pacific war; about 180,000 took part in the assault. Japanese defenders under General Mitsuru Ushijima fought from cave lines in the south, and kamikaze planes sank or damaged hundreds of ships. Estimates vary: about 12,000 Americans and over 90,000 Japanese troops were killed, and some 40,000–150,000 Okinawan civilians died, some in mass suicides urged by Japanese troops. Organized resistance ended June 22.
Why it matters
Its huge toll on all sides weighed heavily on US planning for invading Japan and on the decision to use atomic bombs.
How we know
US and Japanese military records, Okinawan civilian testimony, Okinawa's prefectural archives, and the Cornerstone of Peace memorial, which lists over 240,000 names of the dead of all nationalities.
Still debated
How far the Japanese army ordered Okinawan civilians' mass suicides is politically contested in Japan, notably in a 2007 dispute over school textbook wording.
Connections (4)
▸Battle of Iwo Jima was followed by Battle of OkinawaWell documented
The connection
Iwo Jima ended in late March 1945, and the invasion of Okinawa began April 1. Both were stepping stones toward Japan's home islands, and both showed Japanese defenders shifting from beach defense to deep, fortified positions meant to bleed attackers, making each island costlier than the last.
When and how
Iwo Jima, February–March 1945, and Okinawa, April–June 1945, both in Admiral Chester Nimitz's Central Pacific drive.
How we know
US campaign plans placed both as steps toward invading Japan, and Japanese defense plans show the shared strategy of attrition.
Debates and open questions
Whether either island needed to be taken at such cost has been questioned since 1945.
▸Battle of Okinawa shaped the invasion fears behind the Atomic bombings of Hiroshima and NagasakiMostly agreed
The connection
Okinawa's toll, tens of thousands of US casualties and enormous Japanese military and civilian deaths, shaped US projections for invading Japan's home islands (Operation Downfall). At a June 18, 1945 meeting, Truman said he hoped to prevent 'an Okinawa from one end of Japan to the other', a fear that weighed in using the bomb.
When and how
Washington, June–July 1945: Truman's meeting with the Joint Chiefs on June 18; the first atomic bomb fell on August 6.
How sure are we?
Minutes of the June 18 White House meeting and wartime casualty estimates for the invasion of Japan survive.
Debates and open questions
Postwar claims of half a million to a million American lives saved exceed most wartime estimates, which were lower; the figures remain contested.
▸Proximity fuze defended the fleet against kamikazes at Battle of OkinawaMostly agreed
The connection
Off Okinawa, waves of kamikaze planes attacked US ships for nearly three months. Destroyers and carriers fired 5-inch shells with proximity fuzes, which burst near a plane without a direct hit and were judged several times more effective than older timed shells. They saved many ships, yet about 4,900 US sailors still died.
When and how
Waters around Okinawa, April–June 1945; ships of the US Fifth Fleet, especially radar-picket destroyers, against Japanese suicide aircraft.
How sure are we?
US Navy gunnery analyses rated VT-fuzed shells about three times as effective per round as timed shells, though the ratios vary by study.
Debates and open questions
How many planes the fuze downed, versus fighters and other guns, is uncertain, since gunners on several ships often claimed the same target.
▸Night vision first saw US combat use in the Battle of OkinawaMostly agreed
The connection
US 'sniperscopes,' carbines fitted with an infrared lamp and an image-converter sight, reached Army and Marine units on Okinawa. Japanese troops often attacked or infiltrated at night, and the scopes let defenders spot them in total darkness at short range.
When and how
Okinawa, April–June 1945; small numbers of M1 carbines with M1 and M2 sniperscopes, used by US Army and Marine units.
How sure are we?
Army ordnance reports and veterans' accounts; usually cited as the first US combat use, though Germany's similar Vampir sight saw action in early 1945.
Debates and open questions
Wartime claims that sniperscopes caused a large share of Japanese night casualties are hard to verify and may be exaggerated.