The Pentagon has agreed to release dozens of previously undisclosed photographs depicting the abuse by American military personnel of captives in Iraq and Afghanistan. The pictures, showing incidents at a half-dozen prisons in addition to the notorious Abu Ghraib installation in Iraq, will be made available by May 28, the Defense Department and the American Civil Liberties Union said. These photographs provide visual proof that prisoner abuse by U.S. personnel was not aberrational but widespread, reaching far beyond the walls of Abu Ghraib," said Amrit Singh, a staff attorney with the A.C.L.U., which sued for release of the pictures under the Freedom of Information Act. There were early reports that at least some of the new pictures show detainees being intimidated by American soldiers, sometimes at gunpoint, but Ms. Singh said it is not yet clear what kinds of scenes were captured, and by whose cameras. Disclosure of the latest pictures "is critical for helping the public understand the scope and scale of prisoner abuse as well as for holding senior officials accountable for authorizing or permitting such abuse," said Ms. Singh, who argued the case before the United States Court of Appeals for the Second Circuit, in Manhattan. The Pentagon's decision to release the pictures came after the A.C.L.U. prevailed at the Federal District Court level and before a panel of the Second Circuit. The Pentagon had fought the release of the photographs, connected with investigations between 2003 and 2006, on the grounds that the release could endanger American military personnel overseas and that the privacy of detainees would be violated.