Early this year, military intelligence agents and prosecutors showed up at a white, single-story farmhouse here in southern Taiwan and told Lo Hsien-sheng that they needed to search the premises. They hunted in sacks of rice, burrowed in the garden and checked the chicken pen.

“They said they were looking for money,” recalled Lo, a 52-year-old retired soldier whose younger brother — a senior officer in the Taiwanese military — had just been arrested in Taipei, the capital, and charged with spying for China.

The search was part of a frenzied effort to answer questions deeply troubling to not only Taiwan but also Washington: Why did a successful and seemingly loyal officer in a military rooted in hostility to the Chinese Communist Party turn against his country, and what secrets did he betray?

Until his arrest in late January, Maj. Gen. Lo Hsien-che ran the army command’s communications and electronic information department. This put him at the heart of a command-and-control system built around sophisticated and highly secret American technology that China had been trying to get its hands on for years.

Sentenced to life in prison in July by the Military High Court, Lo is the highest-ranking officer convicted of espionage in Taiwan in decades — and a reminder, according to the Ministry of National Defense, that, despite a recent warming of relations between Taipei and Beijing, “mainland China’s efforts to collect our military intelligence have not stopped but intensified.”

Maj. Gen. Lo Hsien-che in 2007. (REUTERS)

Lo’s spying on behalf of Beijing, which went on for at least seven years, has stirred deep unease, not only because he had access to secrets but also because of his background. The son of a Kuomintang (KMT) soldier who fled to Taiwan in 1949 to escape Mao Zedong’s victorious Red Army, Lo grew up infused with the values that dominate the military establishment of Taiwan, also called the Republic of China.

But what those values are, exactly, has become increasingly confused in recent years as democracy has shaken old certainties and exposed deep divisions between those who favor rapprochement — and even reunification — with the mainland and rivals who want to keep Beijing at arm’s length.

Lo’s motives for spying, said Andrew N.D. Yang, deputy minister of national defense, are under investigation. “It is a jigsaw puzzle. We haven’t reached the final stage yet,” he said in an interview in his office, the walls plastered with military maps of Taiwan and mainland China, which lies just over 100 miles away — and claims Taiwan as its territory.

The case has come at a particularly sensitive time for Taiwan, which will hold a presidential election in January and has spent recent months frantically lobbying Washington for new warplanes. The Obama administration last week unveiled a $5.8 billion arms package for Taiwan that includes sophisticated radar and other equipment to refurbish an aging fleet of F-16 A/B jets. But the White House shows no sign of approving a long-standing request by Taipei for new, more advanced planes.

‘Money and sex’

Taiwan’s government, which was tipped off about Lo’s double game by the United States, has released few details of his treachery. But, through media leaks and occasional statements, it has sought to calm fears that he betrayed Taiwan because of any pro-Beijing ideology or desire for swift reunification.

“His motive was just money and sex — mainly sex,” said Lin Yu-fang, a KMT lawmaker and member of the legislature’s Foreign Affairs and National Defense Committee. This explanation holds that Lo — a married father of three — simply stumbled into a Beijing-sprung “honey trap” while serving in Bangkok from 2002 to 2005 as a military attache.

It was a time of frustration and even anger in Taiwan’s KMT-dominated military and civilian bureaucracies, which worried about the country’s direction under then-President Chen Shui-bian, the island’s first non-KMT leader since 1949. Chen, who left office in 2008 and is now in jail for corruption, alarmed many in the KMT by stressing Taiwan’s separate identity from that of the mainland and by making gestures, mostly symbolic, that tilted toward independence for Taiwan, something that Beijing has vowed to stop at any cost and which the KMT also opposes.

Under Chen, the word “Taiwan” appeared on Republic of China passports, and statues and photographs of Chiang Kai-shek, the KMT’s late leader and a champion of Chinese reunification, vanished from many public buildings.

Lo’s brother, speaking at the family’s farm in his first interview, said his jailed sibling never revealed any sympathy for the Communist Party but didn’t consider it Taiwan’s enemy anymore.

“We were raised on slogans about fighting communists and serving the Republic of China,” said the spy’s older brother. “I know my brother would never betray Taiwan’s interests.”

Beijing, the brother said, “stopped being our enemy” when Taiwan lifted restrictions on travel to the mainland in the 1980s, and their father, along with many other former KMT soldiers, began making trips back to visit relatives.

A history of espionage

Espionage across the Taiwan Strait is hardly new. When the KMT decamped to Taiwan in 1949 — along with tens of thousands of soldiers such as Lo’s father — it left a network of agents behind and has worked to keep intelligence flowing ever since. Meanwhile, Beijing has developed its own network in Taiwan. In August, a court in Taipei convicted a Taiwanese software engineer for trying to obtain information about Taiwan’s U.S.-made Patriot missile defense system from friends in the military.

But Lo’s betrayal has stirred particularly acute alarm. His job gave him access to some of Taiwan’s most closely guarded secrets — involving a new command, control and communications system known as Po Sheng, or “Broad Victory,” long a target of Chinese espionage here and in the United States.

In 2008, former Pentagon employee and Alexandria resident Gregg W. Bergersen pleaded guilty to providing classified information on U.S. weapons sales after the FBI uncovered a Beijing spy ring focused on American military cooperation with Taiwan. One of its main targets, according to an affidavit presented in court, was Po Sheng.

Yang, Taiwan’s deputy defense minister, said the system “has not been compromised” by Lo’s spying, which involved at least five separate transfers of information to, and illicit payments from, a Chinese handler.

But at a recent Taipei conference on security, Jean-Pierre Cabestan, a Taiwan expert at Hong Kong Baptist University, said the case suggested that Taiwan’s espionage and counter-espionage networks are “deeply gangrened’’ by communist agents.

The KMT, which has rapidly expanded Taiwan’s economic and other ties with the mainland since returning to power in 2008, has responded furiously to suggestions that Lo’s betrayal points to a wider rot and that the military can’t keep U.S. secrets safe, insisting that it shows only one man’s weakness in the face of temptation.

Brother points to U.S.

Lo’s brother, however, said he doubts that sex led his sibling astray, noting that Lo was a devout Buddhist and could “control his desires.” He instead blamed his brother’s troubles on the United States, suggesting that he had been set up.

He said Lo returned from a visit to Hawaii with a Taiwan military delegation last year complaining that he’d been approached by unidentified Americans in his hotel and treated “very rudely.” It is not clear who they were or what they wanted, although one former Taiwan defense official said the FBI had tried to turn Lo and recruit him as a double agent.

York Chen, a pro-opposition defense expert, said he met Lo while serving as a senior adviser to Taiwan’s national security council under President Chen. Sex, he believes, “was just a trigger” for deeper grievances against civilian politicians. “To him, the situation looked hopeless,” York Chen said.

Tiehlin Yen, a retired naval captain and a scholar at National Chengchi University’s Center for Security Studies, also met Lo but thinks his treachery was simply a desperate attempt to protect his career after getting trapped in a sexual liaison he wanted to keep quiet. “He had everything. He was a future star,” Yen said.

Shortly before Lo’s arrest, his son enrolled in a Taipei military academy, continuing the family’s military tradition into a third generation. (The son has since been expelled, officially because of poor grades.)

Tsai Jung-ming, a 91-year-old KMT veteran who lives next to the Lo family farm, said Lo used to visit him whenever he came from Taipei to see his mother and brother. They sometimes talked about the trips that Lo’s father had made to see family on the mainland.

China, Tsai said, is “now much richer,” but “I still hate the communists.” He can’t believe that Lo would have spied for them. “One day maybe we will understand — and he will be clean again.”