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There are many other islands in southern Japan that seem large enough for B29 runways (the current runway is 2 miles). Why didn't the USA pick the island of least resistance? I'd assume Okinawa was the most fortified due to its size and local population.

Alternatives to Okinawa

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The Allies weren't taking Okinawa for B-29 runways. They had those already in the Mariana Islands. A B-29 airfield was built on Okinawa, but the first attack from it against Japan happened on the last night of the war.

The primary reason for taking Okinawa was as a base for the invasion of Japan, both for ships and shorter-ranged aircraft. Okinawa has harbours, and Kadena Air Base had already been built by the Japanese.

This required taking all of the Ryukyu Islands, and that's what was done. The Battle of Okinawa is the famous part of this campaign, because the Japanese concentrated their resistance there, knowing that while they held the main island, the other islands would be of limited use. You can't set up mobile fleet bases while the enemy are still within artillery or small-boat attack range. The other islands in the group were taken comparatively easily, so the combats are not famous.

Sources: Okinawa, 1945: Final Assault on the Empire, Simon Foster, 1996 and Okinawa: The Last Battle, the relevant volume of the US official history, available here.

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  • A quick glance at p.419 of history.army.mil/html/books/005/5-11-1/CMH_Pub_5-11-1.pdf might help improve this answer. It would be a shame to waste all those lovely up-votes. :-) – Agent Orange Sep 21 at 10:08
  • @AgentOrange: Better? – John Dallman Sep 21 at 15:02
  • "...the last night of the war." Was this the bombing of Tsuchizaki, which at least in recent years is currently a part of Akita City? – Panzercrisis Sep 22 at 8:31
  • (1) Okinawa was the key island in the Ryukyu group, with the important port, anchorages, existing airbases, and Japanese defenses, as you said. (2) The US wanted bases in the Ryukyus for the invasion of Japan, and for the projection of power into Asia (ie. China), so the B-29 basing was important. (3) Okinawa itself was initially deemed unsuitable for airbase development and a small number of other islands in the group were intended to be occupied in follow-up operations for airbases, including the B-29 base. It was never intended to occupy all the islands in the group. – Agent Orange Sep 22 at 9:55
  • (4) After Okinawa and Ie Shima were occupied it was discovered Okinawa was in fact very suitable for airbase development, and so follow-up operations were cancelled. Only one additional island was occupied (for an early-warning station). The number of airbases scheduled for Okinawa was increased from 8 to 18, including the B-29 base. So I think only three islands in total were occupied in the Ryukyu group. Which brings us back to the original question... I think the importance of the naval bases, and the elimination of the key Japanese defenses in the group were probably the actual reason. – Agent Orange Sep 22 at 10:06
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Okinawa is the largest (by far) of the Ryukyu Islands. Given the importance of these islands, as discussed in the rest of the answer, this made Okinawa the one to own. That is, Okinawa had room for "runways," harbors, and other facilities, in addition to its strategic importance.

A large part of the importance of the Ryuku Islands stems from the fact that it is a chain of islands that more or less link Japan to Taiwan, and points south and west. With the possession of those islands, America could completely cut off the Japanese Home Islands from its possessions in China. Had the atomic bomb not been dropped, the year 1946 might have featured an invasion of Japan simultaneously with the liberation of Japanese held China.

From an "invasion" perspective, the Ryukyus generally, and Okinawa particularly, were close enough to the main Japanese islands for both ships and short-ranged aircraft to be a menace to Japan, and yet not so close as to meet the "main force" of the Japanese defense. This made them an ideal target for a "preparatory" invasion in 1945.

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  • How important was "room" to the USA? Is there an estimate for how much of Okinawa would have been used? – philn Dec 31 '18 at 16:56
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    @philn:Okinawa en.wikipedia.org/wiki/Okinawa_Island has ten times the area of Saipan in the the Marianas, which didn't have quite enough "room" for everything the U.S. needed.Okinawa was also the 5th largest island of Japan (after the four main ones). – Tom Au Dec 31 '18 at 20:46
  • @philn Initially the US was proposing to build just 8 airbases on Okinawa, as the terrain of the island was regarded as largely unsuitable, and they intended to occupy other islands in the Ryukyus in follow-up operations to allow for additional airbases, including basing for B-29s. Having occupied and surveyed Okinawa they soon realized there was a much greater potential for airbase construction on Okinawa itself than had been anticipated. They cancelled the proposed follow-up operations and increased to 18 the number of airbases to be constructed on Okinawa, including the B-29 field. – Agent Orange Sep 21 at 14:03

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