Complex sentence: Sture was mortally wounded at the battle of Bogesund, on January 19, and the Danish army, unopposed, was approaching Uppsala, where the members of the Swedish Riksdag had already assembled.
Split into simpler sentences: Sture was mortally wounded at the battle of Bogesund, on January 19. The Danish army, unopposed, was approaching Uppsala, where the members of the Swedish Riksdag had already assembled.