As a child in South Korea, Ban Ki-moon wrote a letter to the U.N. secretary-general regarding the Hungarian uprising against Russia. A few years later in the United States, he met President John F. Kennedy. From then on, Ban desired to work for peace, an aspiration that led him to become South Korea's foreign minister in 2004, at a time when tensions between North Korea and its neighbors were heated. Two years later, he ascended to the position of...