Pierre François Xavier Boyer became a French division commander during the Napoleonic Wars. He joined a volunteer regiment in 1792. He fought in the Italian campaign of 1796 and participated in the French invasion of Egypt in 1798. He became a general of brigade in 1801 and took part in the Expedition to Saint-Domingue in 1802. While sailing back to France he was captured by the British. After being exchanged, he fought at Jena and Pultusk in 1806, Friedland in 1807 and Wagram in 1809. Transferred to Spain, Boyer led a dragoon division at Salamanca and Battle of Venta del Pozo in 1812 and Vitoria in 1813. He earned the nickname "Pedro the Cruel" for brutal actions against Spanish partisans. He led an infantry division at the Nivelle and the Nive in late 1813. His division was transferred to the fighting near Paris and he was promoted general of division in February 1814. He led his troops at Mormant, Craonne, Laon and Arcis-sur-Aube.

The Battle of Salamanca took place on 22 July 1812. An Anglo-Portuguese army under the Earl of Wellington defeated Marshal Auguste Marmont's French forces at Arapiles, south of Salamanca, Spain, during the Peninsular War. A Spanish division was also present but took no part in the battle.