WASHINGTON — Daniel Ellsberg, the former Defense Department official who leaked the Pentagon Papers during the Vietnam War, is urging government insiders to provide similar classified documents about the invasion of Iraq. Joined by other whistle-blowers and former government employees, Ellsberg said at a Sept. 9 news conference that claims of government deception and lies have “little credibility” unless supported by documentary evidence, which often is available only in classified materials. The document that came to be called the Pentagon Papers was a 7,000-page study of U.S. decision-making in Vietnam that was classified “top secret.” Ellsberg leaked the study to...