Army Pfc. Bradley Manning pleaded guilty Thursday to sending huge digital archives of secret U.S. military and diplomatic records to the WikiLeaks website, saying he was motivated by a U.S. foreign policy "obsessed with killing and capturing people."

Manning, 25, sat erect in dress blues beside his lawyers in a military courtroom and read aloud for more than an hour — slowly but sometimes stumbling over his words — from a 35-page, handwritten statement that described his personal angst over America's wars in Iraq and Afghanistan.

"I began to become depressed with the situation we had become mired in year after year," he said.

After his nearly three years in jail, Manning's sometimes rambling, sometimes riveting confession offered the first public insights into what drove the former low-level intelligence analyst to play a role in what prosecutors called the largest leak of classified information in U.S. history — an estimated 700,000 documents in all.