Another successful operation was his mediation of talks between Swedish envoys led by Karl Otto Mörner and Jean-Baptiste Bernadotte, who was elected Crown Prince of Sweden in August, 1810 and eventually ascended to the Swedish throne in 1818 as Charles XIV John of Sweden. Mutual understanding between Chernyshyov and Bernadotte became an asset in January 1812, during their negotiations about Sweden's stance in the anticipated French invasion of Russia. However, Russian diplomacy failed in recruiting Bernadotte into military coalition, and the talks culminated in the Treaty of Åbo (August 30, 1812), which upheld Sweden's friendly neutrality.