Benjamin Pierce Bishop, 59, is accused of sending the woman an email last May with information on existing war plans, nuclear weapons and U.S. relations with international partners, according to the complaint filed in U.S. District Court in Honolulu.
The complaint alleges Bishop told the woman over the telephone in September about the deployment of U.S. strategic nuclear systems and about the ability of the U.S. to detect other nations' low- and medium-range ballistic missiles.
Bishop originally met the woman at a conference in Hawaii on international military defense issues, the complaint said. It doesn't specify when the conference was held, but it alleges the two began an intimate, romantic relationship in June 2011.
The complaint said the woman was living in the U.S. as a student on a J-1 visa, for people in work- and study-based exchange programs. It's not clear what institution she attended, or where she is now.
Bishop allegedly hid his relationship with the woman from the government even though his position and security clearance requires him to report contact with foreign nationals.
Authorities conducting a covert search of Bishop's home in the Honolulu suburb of Kapolei in November found 12 individual documents marked "secret" even though he's not authorized to keep classified papers at home, the complaint said.
Last month, the woman asked Bishop what western countries knew about "the operation of a particular naval asset of People's Republic of China," the complaint said, though the topic fell outside Bishop's regular work assignments. Bishop researched the issued using open source records and was observed collecting and reviewing classified information on the topic, the complaint said.
Authorities arrested Bishop at U.S. Pacific Command headquarters at Camp H.M. Smith in Hawaii on Friday.
Bishop wore a white jail jumpsuit and was shackled by his wrists and ankles when he appeared in federal court in Honolulu on Monday.
His read and signed some documents with the help of a pair of black-rimmed reading glasses. He had white and gray hair and sported a few days of beard growth.
U.S. Magistrate Judge Richard Puglisi conditionally appointed Bishop an attorney after hearing arguments that his finances weren't sufficient to cover the high costs of defending himself against an espionage charge.
Bishop faces one count of communicating national defense information to a person not entitled to receive it and one count of unlawfully retaining national defense documents and plans.
Bishop's court-appointed attorney, Birney Bervar, said Bishop is a lieutenant colonel in the U.S. Army Reserve.
"Col. Bishop has served this country for 29 years. He would never do anything to harm the United States," Bervar told reporters after Bishop was formally presented with the charges.
Bishop is scheduled to appear in court Friday for a hearing on whether he will remain in detention during the case. A preliminary hearing is scheduled for April 1.