The vast number of islands that were invaded/recaptured by the Allied forces were not highly occupied by civilian populations. Iwo Jima had virtually no inhabitants. Very different experiences were encountered on Saipan, in the Philippines, and on especially on Okinawa whose pre-invasion civilian population was estimated at 300,000 people. Okinawans were Japanese citizens, at least in law.

After the 1879 annexation of the Ryukyu Kingdom, Okinawa was made a prefecture of Japan. By the time of the Allied landings, Okinawans were Japanese citizens in law: subject to conscription, taxation, and wartime mobilization like all other Japanese. Their cultural and social status was something different. The longer and deeper roots of Okinawa were Chinese in custom and perspective and as a result, Okinawans were often regarded by mainland Japanese as a peripheral or inferior people, with distinct language, customs, and history. The Okinawan (Ryukyuan) language was suppressed in schools in favor of standard Japanese. Children caught speaking Okinawan dialects were sometimes punished. Mainland Japanese officials and soldiers stationed in Okinawa frequently treated locals as less disciplined, less loyal, or “not quite Japanese.” 

Prior to 1944, Okinawans could join the Japanese military but were rarely assigned to combat ranks, most often serving in labor units, auxiliary roles, or support services. After the fall of Saipan in July 1944, Japan recognized that Okinawa was likely to be the next U.S. target. At that point the 32nd Japanese Army was stationed on Okinawa, and the Japanese authorities began mass mobilization of the Okinawan population. The mobilization had three primary elements:

The Battle of Okinawa which began with the initial invasion on 1 April 1945 was the largest amphibious assault in the Pacific Theater of World War II. It was the bloodiest battle of the Pacific War. The most complete tally of deaths during the battle is inscribed on the Cornerstone of Peace monument at the Okinawa Prefecture Peace Memorial Museum, which identifies the names of each individual who died at Okinawa in World War II. At the time of the June 1995 unveiling 234,183 names were inscribed. Continued historical research leads to the addition of names. Today, the monument lists more than 242,000 names, including 149,634 Okinawans; 77,823 Imperial Japanese soldiers; 14,010 Americans soldiers, Marines and sailors; and smaller numbers of people from other countries.

What is little known is that more naval personnel (4,907) were killed in action than either Army (4,675) or Marine (2,938) soldiers.

Iwo Jima is a small volcanic island about 750 miles south-southeast of Tokyo. The island had two operating airfields from which flew Japanese fighters and bombers. From late 1944 to early 1945, the Japanese stationed fighters and bombers on Iwo Jima. Their mission was to intercept the U.S. B-29s bombing Japan and to conduct night bombing raids on the Mariana airfields to disrupt U.S. bombing operations. Japanese bombers conducted about nine significant raids against the Marianas. The night raids were small in scale,  typically 5 to 20 Mitsubishi G4M “Betty” bombers. The raids never seriously curtailed B-29 missions as U.S. forces had ample construction battalions to repair damage quickly. The Japanese air raids from Iwo Jima on the Marianas were annoying but not decisive. Their main effect was psychological and tactical, not strategic.

The island lay virtually under the direct flight path to Tokyo of B-29 bombers operating out of Saipan and Tinian allied airfields. The direct distance was 1,350 miles but in order to avoid Iwo Jima’s fighters, the flight route was 1,700 miles one way. Despite the route, the island served as an early warning station for Japanese mainland defense.

The strategic reason for invading and taking Iwo Jima was to eliminate the early warning capability, the fighter intercepts on the bombers, the nuisance bombing raids on B-29 bases, shorten the route to/from the Japanese home islands for the “finicky” B-29s, and provide an emergency diversion landing site for returning B-29 bombers. This last feature came into use during the intense fighting on Iwo Jima and by war’s end was responsible for saving ~2,400 US Army Air Force pilots and flight crews.