Appointed at the age of sixteen to
acting sub-lieutenant in the
Fleet of the Army, Rajalin served 1780–82 as an employee of the
French Navy. After having returned to Sweden, he quickly rose through the ranks and became, since the
Caribbean island of
Saint Barthélemy in 1784 came into
Swedish possession, in 1785 the first Swedish governor there. From there he was transferred in 1787 to the governor location on
Gotland and held that post for 20 years, during which he however long periods of time held different positions of trust. He was during the
Russo-Swedish War 1788–90 military commander of the
Archipelago fleet and excelled particularly in an engagement at
Porkkalanniemi on 26 August 1789. After the peace treaty he became rear admiral in 1791 and was 1791–94 general commissary in the fleet. Appointed vice admiral in 1799, Rajalin was 1801–09 as acting adjutant general, rapporteur before the king in cases involving the fleet. During the
Finnish War in 1808 he commanded the Archipelago fleet, but resigned from this position in October of that year. Appointed in 1809 by
Charles XIII to admiral, he became in 1812 governor of
Gävleborg County, but resigned already in 1813 from this position. ==Personal life and death==