Battle of Okinawa - Wikipedia

On June 21, 1945, Japanese forces on Okinawa surrender to American troops. From the article:

"Ninety percent of the buildings on the island were destroyed, along with countless historical documents, artifacts, and cultural treasures, and the tropical landscape was turned into "a vast field of mud, lead, decay and maggots".[85] The military value of Okinawa "exceeded all hope". Okinawa provided a fleet anchorage, troop staging areas, and airfields in proximity to Japan. The US cleared the surrounding waters of mines in Operation Zebra, occupied Okinawa, and set up the United States Civil Administration of the Ryukyu Islands, a form of military government, after the battle.[86] In 2011, one official of the prefectural government told David Hearst of The Guardian:

You have the Battle of Britain, in which your airmen protected the British people. We had the Battle of Okinawa, in which the exact opposite happened. The Japanese army not only starved the Okinawans but used them as human shields. That dark history is still present today – and Japan and the US should study it before they decide what to do with next.[87]

Effect on the wider war
Because the next major event following the Battle of Okinawa was "the total surrender of Japan," the "effect" of this battle is more difficult to consider. Due to the surrender, the next anticipated series of battles – an invasion of the Japanese homeland – never occurred. (Therefore, all military strategies on both sides which presupposed this apparently-inevitable next development were immediately rendered moot.)

Some military historians believe that the Okinawa campaign led directly to the atomic bombings of Hiroshima and Nagasaki, as a means of avoiding the planned ground invasion of the Japanese mainland. This view is explained by Victor Davis Hanson in his book Ripples of Battle:

... because the Japanese on Okinawa ... were so fierce in their defense (even when cut off, and without supplies), and because casualties were so appalling, many American strategists looked for an alternative means to subdue mainland Japan, other than a direct invasion. This means presented itself, with the advent of atomic bombs, which worked admirably in convincing the Japanese to sue for peace [unconditionally], without American casualties.

Meanwhile, many parties continue to debate the broader question of "why Japan surrendered", attributing the surrender to a number of possible reasons including: the atomic bombings,[88][89][90] the Soviet invasion of Manchuria,[91][92] and Japan's depleted resources."