Frederick, the Danish crown prince, had urged the Norwegian people to write
their own constitution in May 1814. He also tried to move the Norwegians
to oppose the surrender of Norway to Sweden and rebel against the Treaty
of Kiel. However, his skills as commander general proved inferior to his
skills as an orator. When the Swedes crossed the border to Norway in July
the same year, the Norwegian resolve crumbled. Carl Johan, who led the
Swedish campaign, did not want a brutal war since he thought it probable
that he would soon take over as king in Norway. When Norway surrendered
in August, Sweden committed itself to recognising the Norwegian constitution
as valid despite the union with Sweden.
In October a resolution was passed accepting the union with Sweden and in November Carl XIII was elected king of Norway. Carl was then well into his sixties. He had witnessed his older brother Gustav III's coup d'état in 1772 and his assassination in 1792. He had served as guardian for Gustav's son, Gustav IV Adolf. When Gustav IV Adolf was deposed, Carl was elected king. However, Carl did not take too great an interest in his royal duties, and pretty much left it to his councillors to run the country.
Carl XIII was childless. Therefore, a successor was elected.
Initially, this was Carl August, formerly Christian August of Augustenborg.
However, Carl August died in 1810, and Carl Johan
was then appointed as the successor to Carl XIII. When Carl XIII took over
as king in Norway in 1814, Carl Johan had already been de facto ruler of
Sweden for four years. Though formally King of Norway until his death in
1818, Carl XIII never set foot in Norway.