(This story was corrected in paragraph 8 and 9 to reflect that Gen. Carr was referring to a claim by the Taliban and said that the Afghan's name was not in Manning's material)
By Tom Ramstack
FORT MEADE, Maryland (Reuters) - The U.S. Army was overwhelmed when WikiLeaks published more than 700,000 secret diplomatic and war documents handed over by soldier Bradley Manning, a retired officer testified in the sentencing phase of the convicted private's court-martial.
"The ones that hit us in the face were the Iraq logs," retired Brigadier General Robert Carr said in a Fort Meade, Maryland court on Wednesday, a day after a military judge found Manning guilty of 19 charges over the leaks in 2010, the biggest breach of classified data in U.S. history.
"No one had ever had to deal with this number of documents," Carr said.
A prosecutor told the sentencing hearing that the leaks caused military intelligence officials to rethink how much access to allow low level intelligence analysts like Manning.
Judge Colonel Denise Lind began hearing arguments on Wednesday on how long a sentence he should face, with the soldier's lawyers expected to argue for leniency.
While Manning, 25, was acquitted on the most serious charge of aiding the enemy, sparing him life without parole, he could still face decades in a military prison.
The slightly built Army private first class was in Baghdad in 2010 when he was arrested and charged with leaking files including videos of a 2007 attack by an American Apache helicopter gunship in Baghdad that killed a dozen people, including two Reuters news staff, diplomatic cables, and secret details on prisoners held at Guantanamo Bay.
Carr testified that Taliban militants in Afghanistan had claimed that the leaks allowed them to track down a citizen of that country who had worked with U.S. intelligence. "The Taliban killed him and tied him to the disclosures," Carr said.
However, he said, the Afghan's name was not in the material that Manning revealed.
Manning's lawyers were expected to argue that the Army private was not trying to jeopardize U.S. national security. He did not testify during his trial or during the first day of his sentencing hearing.
A prosecutor, Major Ashden Fein, said Manning's leaks "have impacted the entire system" for granting defense analysts access to classified information.
Some observers pointed out that the case of Manning, as well as that of former CIA security contractor Edward Snowden, illustrated the risk inherent in granting security clearance so broadly. Snowden last month released to media documents detailing U.S. programs to monitor phone and internet usage.
U.S. intelligence agencies grant analysts broad access to classified files in hopes that they will connect disparate pieces of evidence to interpret events and avoid the sort of lapses that led to clues being overlooked before the September 11, 2001 hijacked plane attacks and the bombing of the Boston Marathon in April.
"As with any type of computer database and security, the weakest link is the person who's operating it," said Scott White, a professor of homeland security management at Drexel University in Philadelphia.
There is a risk in restricting access, he said: "Do you slow the intelligence process down by putting more and more limits on your own people?"
In a court martial that stretched over two months, military prosecutors had argued that Manning became a "traitor" to his country when he handed over files to WikiLeaks, thrusting the anti-secrecy website and its founder Julian Assange into the international spotlight.
Observers said the verdict could have "a chilling effect" on WikiLeaks by making potential sources of documents in the United States more wary about handing over secret information.
It could also encourage the United States to seek to prosecute Assange for his role in publishing the information.
Assange has been living in the Ecuadorean embassy in London for over a year to avoid extradition to Sweden, where two women have accused him of sexual assault. The activist says he fears Sweden might hand him over to U.S. authorities.
Writing by Scott Malone; Editing by Grant McCool