US military facilities across the southern Japanese prefecture of Okinawa are critical to Washington's security commitments in the western Pacific, with the Kadena Air Base, in particular, considered the "lynchpin" of US air power in the region.
The base, one of the largest US military installations, is home to the US Air Force's 18th Wing, the service's largest and most diverse combat wing operating a range of fighter jets from the F-15 Eagle to the F-22 Raptor, as well as reconnaissance, early warning and refueling aircraft.
The installation was crucial to US air operations during both the Korean and Vietnam conflicts in the past, and is similarly critical to fending off an increasingly aggressive rival: China.
Kadena is located just 443 nautical miles from Shanghai and even closer to the northern tip of Taiwan. The air base will be on the frontlines should China decide to try to use force to seize control of Taiwan, which Beijing claims as its own territory.
'Keystone of the Pacific'
"Kadena is the keystone of the Pacific and the mission of the 18th Wing is to reassure our allies and partners, deter regional aggression and defend the first island chain," said a US Air Force officer, who asked not to be named.
Managing tensions in the South China Sea
The first island chain refers to the area that runs from Japan through Taiwan, the Philippines and on to Borneo, enclosing China's coastal seas.
While China sees breaking through the first island chain as an important goal, the US and its allies want to contain the Chinese military within the island chain and make it difficult for Chinese naval vessels to freely sortie into the Pacific Ocean without being monitored and, in the event of a conflict, attacked.
Aircraft from Kadena regularly carry out operations over the South China Sea, where Beijing's forces have unilaterally occupied and fortified small islands claimed by a number of other nations.
The US air force official said that US air operations in the region take place in "international air space to ensure that the international rules-based order is being followed." And, they added, that intercepts between US and Chinese warplanes "are not uncommon" across the Western Pacific.
A key strategic position
"Okinawa is situated at a very reasonable position for any kind of military action in the Western Pacific, from the Korean Peninsula all the way down to the South China Sea," said Michael Cucek, a professor of international relations at the Tokyo campus of Temple University.
"Kadena is the lynchpin of US air power in this part of the globe and, crucially, is close to Taiwan and China and provides air cover over all of southern Japan as well," he told DW.
The US presence in Okinawa goes far beyond the Air Force, however, with the other arms of the military — the US Marine Corps, the US Army and the US Navy — also working closely with Japan's Self-Defense Forces and other partners, from the Indo-Pacific and further afield.
In recent years, that cooperation has involved German, British, Dutch, Australian, French and Canadian units, among others.
Thousands of US Marines in the prefecture
The US Marine Corps' Third Marine Expeditionary Force is headquartered on the Futenma Air Station, a few kilometers south of Kadena, with around 18,000 personnel presently stationed at seven bases across the prefecture.
"We are a forward-deployed force in readiness and we could not be a rapid reaction force if we were not stationed here in Japan," a Marine Corps officer told DW.
"Our government has made it very clear that China is the threat and we are in a position to respond whenever necessary in the region," the officer said.
The Marines on Okinawa are also going through a number of changes in how they will operate in the near future, shifting to a lighter, more agile force that can respond to emergencies at short notice.
Another officer said the Marine Corps is "shifting from being training-focused to being contingency-focused, something that was not in the mission statement just five years ago."
And that is a result of "China's nefarious activities in the region, North Korean saber-rattling, and Russia's strong forward stance to the US."
US, Japan and South Korea to deepen security ties
The US Army presence on Okinawa is relatively small, given that it is primarily designed as the arm of the military that operates on land, although it does operate a network of Patriot anti-missile systems on installations across the prefecture.
Similarly, the US Navy's Seventh Fleet is largely headquartered at the Yokosuka Naval Base, around 60 kilometers (37 miles) south of Tokyo, and the large facility at Sasebo, on Kyushu.
Okinawa will be the ‘frontline'
"The expansion of the military presence shows the US' full commitment to being a power in the Western Pacific and beyond," said Cucek. "The US was forced to leave its previous pivot points in the region, Clark Air Base and the US naval base at Subic Bay in the Philippines in the early 1990s, and so has moved to Okinawa."
And given the pressure that China is gradually ramping up on the government in Taiwan and Beijing's frequently implied threat that it will use force to seize the island, Cucek said, the importance of US forces in Okinawa cannot be overstated.
"If China chooses to try to neutralize US forces as part of an attack on Taiwan, then Okinawa will be the frontline," he said. "The moment that any kind of shooting starts, then the US will be involved and there will be no chance of avoiding a wider war that will also involve Japan."
Edited by: Srinivas Mazumdaru