Ronen Zilberman / AP file The submarine USS Greeneville is escorted to the submarine base at Pearl Harbor, in February 2001. A high concentration of important military commands and facilities on the island mean there's a great deal of information in Hawaii that potential adversaries want to know.

Clandestine agents. Foreign spies. Intelligence. Hawaii is better known for sunbathing on the beach or surfing than high-stakes sleuthing.

But the case of a 59-year-old civilian defense contractor accused of giving military secrets to his much younger Chinese girlfriend is a reminder of the state's little-known identity as a prime target for espionage. A high concentration of important military commands means there's a great deal of information on the islands that potential adversaries want to know.

Case in point: Most of the FBI's resources in Hawaii are concentrated on counterintelligence — not drug trafficking or terrorism.

"One of the FBI's priorities in Hawaii is keeping America's secrets safe from agents of foreign powers," said Tom Simon, a special agent in Honolulu. "With the amount of military and classified material in Hawaii, it remains a top priority for the FBI."

It helps that the state, population 1.4 million, isn't a hotbed of violent crime. That allows agents to focus much of their efforts on thwarting spooks.

The case against Benjamin Bishop, a defense contractor working for the U.S. Pacific Command when he was arrested March 15, offers a glimpse of the information potential adversaries might be looking for.

Bishop knows U.S. secrets on countering weapons of mass destruction, nuclear deterrence and ballistic missile defense, according to a declaration filed in court by Maj. Gen. Anthony Crutchfield, the Pacific Command's chief of staff.

More recently, Bishop worked on cyber security and is familiar with how the U.S. would counter adversaries in electronic warfare, air combat, undersea warfare, energy security and cyberspace, the declaration says.

Investigators say Bishop gave his girlfriend — a 27-year-old graduate student he met at an international military conference in Hawaii— classified information on nuclear weapons, war plans and missile defense.

Bishop hasn't been charged with outright espionage, which the law defines as giving national security secrets to someone for the purpose of helping a foreign government or harming the United States. But he has been charged with two violations of the Espionage Act: communicating defense secrets to someone not entitled to receive it and unlawful retention of defense documents.

Prosecutors haven't said they believe the girlfriend is working for the Chinese government or that she's given anything she learned from Bishop to anyone else. But an FBI affidavit filed in support of the charges speculates she may have attended the military conference specifically to target people like Bishop who work with classified information.

Bishop has not yet entered a plea, but his lawyer says his client wouldn't do anything to harm the U.S. The attorney, Birney Bervar, says the case isn't about espionage but about two people in love.

History of espionage

Spying isn't new to Hawaii.

In the months before the attack on Pearl Harbor on Dec. 7, 1941, a Japanese vice consul in Honolulu spent much of his time monitoring and reporting back home on the comings and goings of the U.S. Navy. Takeo Yoshikawa is said to have favored the view of Pearl Harbor he would get at a tea house — still in business today as the Natsunoya restaurant — in a hilly neighborhood overlooking the naval base.

The Soviet Union kept an intelligence collecting ship off the coast of Oahu during the Cold War to monitor U.S. military communications, said Ralph Cossa, president of Pacific Forum Center for Strategic and International Studies.

Today, the FBI says countries from the Asia-Pacific region are the ones most likely to attempt to gather intelligence about U.S. military operations in Hawaii.

China would have the biggest interest, followed by Russia, Cossa said. North Korea would be interested but doesn't have as many resources.

Their targets? Pacific Command is the U.S. military's headquarters for the Asia-Pacific region. The Navy, Air Force, Army and Marine Corps also each have their own headquarters for the Pacific on Oahu. The National Security Agency keeps an intelligence center tucked away in central Oahu.

There's a major missile defense testing site on Kauai. A high-powered missile defense radar capable of tracking a baseball-sized object 2,500 miles away — called the Sea-Based X-band Radar — visits Pearl Harbor regularly.

These days, computer hacking and cyber espionage — the area Bishop was working in most recently — are major spying methods.

Eyes and ears are useful too, whether they belong to undercover agents or to businessmen, tourists and students who may share what they see with their governments.

Honolulu has nearly 1 million residents, and the state is a mecca for sun-seeking tourists from around the world. This makes Hawaii an easier place for intelligence gatherers to blend in than, say, remote parts of Wyoming where the U.S. keeps ballistic missiles.

Pressure to gather intelligence from the islands is likely growing as the Obama administration places a greater emphasis on the region with the military's "pivot" to the Pacific. Cossa said the policy "shines a big target" on Hawaii.

"I'm sure every intel guy in China has been told 'Get more details. What does it really mean?,'" said Cossa, who spent 26 years in the Air Force, including three tours at Pacific Command.

The reconnaissance goes both ways. On the other side of the Pacific Ocean, the U.S. is eager to gather its own intelligence on new ships, planes and other equipment China is adding to its military.

Cossa said allegations like those against Bishop make for flashy headlines but account for a small percentage of the spying going on.

Most of the espionage involves people trying to listen to phone conversations and hack into email and computers, he said. It's easier for people to steal information this way and it's harder to detect.

"Obviously if you're working with classified information in the military, in Hawaii, you should expect somebody is trying to listen, someone is trying to copy," Cossa said.