After the
capture of Valdivia,
Lord Cochrane departed, leaving Colonel
Jorge Beauchef as commander and governor of
Valdivia. Beauchef decided to head south in order to secure
Osorno, to expel the remains of the royalist forces from the Chilean mainland and to take possession of the area south to the
Maullín River, so that the Spanish would not be able to reoccupy Valdivia by land. His main worry was a possible regrouping of the Royalist forces in the area, since they far outnumbered his own. Beauchef and his small army arrived at
Trumao where they were aided by local
Mapuche-Huilliche who ferried them over
Bueno River and provided the Spanish with
ox carts. Beuchef reciprocated by giving the Mapuche-Huilliche liqueur and
indigo dye which he had brought with him for this end. This support was in breach with the
Parliament of Las Canoas where Mapuche-Huilliche had agreed to support Spain against its enemies. Previous to this battle, all the royalists garrisons that had managed to escape from the cities of Valdivia and Osorno gathered at the
Carelmapu Fort. The governor of
Chiloé Brigadier
Antonio de Quintanilla was disgusted with the poor performance of the old colonel
Manuel Montoya and replaced him with
Gaspar Fernández de Bobadilla and captain
Miguel Senosiaín, and ordered them to return north and combat the patriots. Bobadilla and Senosiain re-crossed the Maullín River at the head of 300 soldiers. ==The battle==