On 15 August 1652, Coenraad van Beuningen left for Sweden, charged by the States General with the important task of persuading Sweden to side with the Dutch Republic in its conflict with England, later known as the First Anglo-Dutch War. Van Beuningen was thirty years old and by no means a professional diplomat. The grandson of an Amsterdam burgomaster, he had been appointed secretary to the Amsterdam town council in 1643 and to the highly influential post of pensionary (chief municipal magistrate and legal adviser) in 1650. This made Van Beuningen the most important adviser to the Amsterdam authorities and, by virtue of his office, a member of Amsterdam's delegation to the States of Holland. Van Beuningen thus combined a position in local government with a role in foreign policy. As a public servant in the employ of the city of Amsterdam, he was naturally a prominent figure in local politics, and his ambassadorial travels in the service of the Republic lent him both national and international prestige.

Although Van Beuningen's two-year stay in Sweden was not in fact successful, he was asked to travel to Scandinavia again, in January 1656, to safeguard the Republic's interests in the war between Sweden and Poland. In this case the Republic's interests largely coincided with those of Amsterdam, the centre of the grain trade with the Baltic. Because Van Beuningen had, in the interim, been unable to devote enough time to his duties as pensionary, he decided to resign his office.