Nearing the end of their case, prosecutors in Fort Meade on Monday tried to prove one of the gravest charges against Pfc. Bradley Manning: that the Army private, who gave WikiLeaks hundreds of thousands of diplomatic and military documents, aided the enemy. The government argued that members of Al Qaeda had sought information made available online by the antisecrecy group after Private Manning’s leak, the largest disclosure of confidential materials in American history. Among the evidence were letters written by Osama bin Laden, discovered during the May 2011 raid on his compound in which he was killed, requesting materials from WikiLeaks. Also Monday, prosecutors called a counterintelligence adviser from the Defense Intelligence Agency, saying he would be their last witness. After the witness answered questions about his background, the judge closed the court for classified testimony. The trial will resume Tuesday. Once the government rests its case, the defense will present its evidence.