Complex sentence: In 1451, the Count of Ourém was made Marquis of Valença and escorted Infanta Leonor of Portugal to her husband Frederick III, Holy Roman Emperor, and later, in 1458, participated in the capture and conquest of Alcácer-Ceguer.
Split into simpler sentences: In 1451, the Count of Ourém was made Marquis of Valença and escorted Infanta Leonor of Portugal to her husband Frederick III, Holy Roman Emperor. Later, in 1458, he participated in the capture and conquest of Alcácer-Ceguer.