This I Believe. Dag Hammarskjöld is Secretary General of the United Nations. He comes from a family with a strong tradition of public service, and is a son of Sweden's World War I prime minister. After teaching political economy at Stockholm University, he went into the civil service, becoming Undersecretary of the Treasury and Chairman of the Bank of Sweden. After World War II, he was attached to the Ministry of Foreign Affairs, and was active in the Organization for European Economic Cooperation. Until his election as Secretary General in 1953, he headed the Swedish delegation to the United Nations.