Last year, John R. Bolton, then U.S. ambassador to the United Nations, recruited Mark D. Wallace as the U.S. representative for U.N. management and reform. Given that Bolton was a longtime critic of the U.N. bureaucracy, no one expected that Wallace would go meekly about his new job. And he didn't. He has met with informants eager to spill bureaucratic secrets, scrutinized internal audits and butted heads with U.N. officials he suspects are blocking his efforts to uncover corruption in development programs in places including North Korea and Burma. (snip) The new U.S. ambassador to the United Nations, Zalmay Khalilzad,...