Complex sentence: Frustrated during the early part of his career by the need to paint portraits to earn a living, Ingres fulfilled his ambition to be recognized as a history painter when his "The Vow of Louis XIII" achieved a triumphant success at the Salon of 1824.
Split into simpler sentences: Frustrated during the early part of his career by the need to paint portraits to earn a living, Ingres was determined to succeed in the more prestigious genre of history painting. His ambition was fulfilled when his "The Vow of Louis XIII" achieved a triumphant success at the Salon of 1824.