US bases occupy a significant amount of land in Okinawa's main island
Okinawa prefecture is made up of dozens of islands that lie at the southern end of the Japanese archipelago.
The region was once known as the Ryukyu islands, an independent kingdom trading across Asia. Islanders spoke Ryukyu languages, some linked to southern Japanese dialects.
In 1609 the Satsuma clan, based on the southern Japanese island of Kyushu, invaded and made the Ryukyu kingdom a tributary. Two and a half centuries later the kingdom was annexed to the Japanese nation.
In the early part of the 20th Century, most residents were fishermen and farmers. The capital, Naha, was on the main island of Okinawa, a long, narrow strip of land covered in mountainous forest in the north.
But the outbreak of World War II was to have a dramatic effect.
As the war ended Allied forces needed a secure base from which to launch an attack on the Japanese mainland. They landed on the main island of Okinawa in April 1945, sparking fierce fighting.
By the time US forces controlled the island three months later, 12,000 US soldiers had been killed and 38,000 injured. More than 100,000 Japanese troops were killed.
Okinawan civilians caught up in the fighting paid a very severe price. According to the Okinawa Prefectural Museum, as many as 100,000 died.
Some starved to death, others were urged - some say forced - by Japanese troops to commit suicide as US victory neared.
After the Japanese surrender, Okinawa was placed under US administration for almost three decades.
America took over Japanese bases and began stationing troops in the region. The US then signed a security pact with Japan, undertaking to defend it in return for land for its military forces.
The Communist take-over in China and eruption of conflicts in Korea and later Vietnam served to emphasise Okinawa's strategic importance to the US.
Planes based in Okinawa flew missions to both Korea and Vietnam. Naval forces were also based there, the region acting as a key hub for the conflicts.
In 1972 Okinawa reverted to Japanese control, but the bases remained.
Today of the 47,000 US troops stationed in Japan, more than half are based in Okinawa. Regional concern over China means that Okinawa remains a key US strategic asset.
Since World War II the main island had changed significantly and anti-base sentiment has been rising.
Anti-base sentiment has grown in recent years, prompting protests
The US bases occupy about 19% of the main island, according to the prefectural government, and population centres in the south are cramped.
Some Japanese land owners object to the US use of their land, while those living near the bases complain about aircraft noise.
Many jobs are linked to the US bases and tourism has boomed, but otherwise Okinawa remains one of the poorest parts of Japan.
The 1995 rape of a 12-year-old Japanese girl by three US servicemen triggered anti-base protests across the island, the largest in more than three decades.
Subsequent incidents have meant that the Okinawa issue has remained in the spotlight, and in 2006 Japan and the US agreed a deal on reducing the US troop presence.
Under the deal, 8,000 US marines will be relocated to Guam, with the Japanese government to pay 60% of the cost. The controversial US airfield at Futenma will be closed and replaced by two new runways in the north of the island.
But some residents say that is not good enough. Residents of the area that would host the new base are opposed to the idea - and their stance has so far prevented the plan moving ahead.