Prior to the
fall of Talca in early March,
Juan Mackenna had been positioned along the rata
Itata river with a small division of patriot troops, whilst
Bernardo O'Higgins had remained with the main body of the army in
Concepción. After
Talca fell to Royalist forces, however,
Mackenna realised his lines of communication with
O'Higgins were now cut and that he was isolated.
Mackenna, the colonel of engineers on the patriot General Staff, formed a solid defensive position, building three mutually supporting
bastions on local hills on the north bank of the north side of the
Itata river near Membrillar. The Royalist commander,
Gabino Gaínza, had sent a vanguard of 400 men into the hills of
Quilo, south of the
Itata river, to prevent the two patriot commanders from reuniting. This force had been defeated in the
Battle of El Quilo on the 19 March, forcing
Gaínza to attempt a different plan.
Gaínza instead decided to attack
Mackenna's forces immediately, before then turning on
O'Higgins.
Chillán sent additional reinforcements, and
Gaínza then crossed the
Itata to attack. ==The battle==