NAHA, Japan — Satoshi Yamamoto took his daughter to the edge of the U.S. Air Force's busiest runway in the Pacific on their summer vacation, hoping to give her a thrill while taking a look at the front lines of a military standoff in the western Pacific.
It worked for his daughter, who declared herself ready to enlist in the American military when she saw four fighter jets successively roar into the skies of the East China Sea.
Yamamoto looked just as excited, but he turned sober when he described why he wanted to spend a day watching jets take off from an American base on Okinawa, the fortified Japanese island that sits closer to Shanghai than Tokyo.
"If the American bases were not here, then China might take over Okinawa," the 52-year-old banker from Tokyo said.
He's one of many Japanese nervously eying China's push into the nearby South and East China seas, where Beijing has rapidly expanded islands for its own military bases and staked claims in international waters.
A fear of conflict in those is driving Japan to swell its defense spending and lending a sense of urgency to the "Pacific pivot," which the Obama administration announced four years ago to refocus the American military after long wars in Iraq and Afghanistan. On Okinawa, that buildup is as tangible as the headquarters for a new Japanese air force squadron, on a runway that already lights up almost twice a day with fighter jets rushing off to intercept Chinese planes testing Japan's airspace.
"This is real world," said Marine Capt. Caleb Eames, an American military spokesman here.
Japan is bulking up with new conventional weapons and searching for amphibious training grounds where it can practice the kind of beach assaults it may need to take an island. Its main ally, the United States, is matching the moves by steering more troops and newer weapons to the Pacific.
And Japan is signaling for the first time since World War II it's ready to use the expensive military it's building as a hedge against China.
In September, its Parliament lifted longstanding military restrictions that would allow it go to war to protect allies instead of solely to defend Japan. That means it can fight alongside the U.S. and other friendly countries if they come under attack in the region.
"The military expansion in China affects every country, not only Japan, not only the countries near the South and East China Sea. It's important for everyone to get China engaged and check their military," said Japanese lawmaker Taro Kono, a member of Prime Minister Shinzo Abe's Liberal Democratic Party who has supported Japan's efforts to create a more muscular military.
To the U.S. and its partners in the Pacific, the buildup represents a counterweight to China's swelling defense spending, which is reported to be climbing at a rate of 7 percent a year.
Since 2013, China added some 2,900 acres of land to atolls in the South China Sea, laying what appears to be an airstrip on at least one of the islands, according to the Pentagon. That expansion puts it in conflict with Vietnam, Malaysia, Taiwan and the Philippines.
A similar conflict is playing out in the East China Sea, where China and Japan have competing claims to a group of islands known as the Senkaku in Japan and the Diaoyu in China.
Despite the palpable sense of concern over China's military expansion, the Japanese and American countermoves stoke fears in both countries that they may be too costly and ultimately could trigger the kind of conflict its proponents hope to prevent.
"They're going to make a new base, and it's going to have the latest technology," said Miyumi Shiroma, 36, who in August joined a protest against a Japan-supported expansion of one of the U.S. Marine bases on Okinawa. "That means Okinawa is going to be a target for a military attack. I don't want our children and grandchildren to live with the most dangerous base in the world on this island."
In Washington, questions still linger whether the U.S. can afford its share of the buildup the Obama administration announced in 2011 as a "Pacific pivot" while the military remains tied to conflicts in Iraq and Afghanistan.
Some are also concerned the U.S. efforts in the region may be contributing to a "spiraling escalation" of military power. The Navy plans to place almost two-thirds of the 300-ship fleet it expects to have by 2020 in the Pacific, breaking from a traditional even split between Pacific- and Atlantic-based fleets.
"It is inflaming an already intense situation. Adding U.S. military power to this situation encourages China to boost its military spending," said David Vine, an American University professor who recently published a book, "Base Nation," that analyzes the costs of the U.S. military's foreign bases.
The military's ability to live up to its commitments in the region depends partly on whether the Navy can keep pace with an aggressive shipbuilding plan that would raise the size of the fleet from today's 273 ships to more than 300.
That's expected to cost an average of $16.7 billion a year for 30 years, according to the Navy. The Congressional Budget Office in late 2014 called that estimate too low, projecting a total cost closer to $21 billion a year.
Another obstacle to the buildup comes from residents on Pacific islands that have held a continual presence of U.S. Armed Forces since the end of World War II. They're losing patience with a military expansion they believe will harm their way of life while making them a more probable target if war ever breaks out.
"We're just part of this big plan in the Pacific," said Leevin Camacho, 37, an attorney on Guam who wants the Pentagon to reduce its footprint on his island. "They use the South China Sea as a justification for all these projects."
He's one of the founding members of We Are Guahan, a group of mostly young Guam natives who in 2010 filed a lawsuit against the Defense Department, challenging a proposal that would have swelled Guam's population, seized privately owned land and disrupted a protected site that holds an ancient village by placing a machine gun firing range next to it.
Back then, the idea was for the Pentagon to get as many Marines to Guam as fast as possible, so it could reduce the number of troops at bases in urban parts of Okinawa while keeping them close to where they may be needed in an emergency.
Japan supported the shift; this year it has spent $56.1 million to pay for Japan-based American military units to train on Guam. It also has agreed to pay for more than a third of the Marine relocation to Guam.
The activists' lawsuit compelled the Pentagon to rewrite its plans for Guam. The newer version, adopted this summer, calls for fewer Marines and does not disturb the archaeological site.
Many residents on Guam and Okinawa insist the Pentagon would never even propose such a massive project in the mainland United States, where voters would compel the Defense Department to balance military training with its impacts on civilians.