Complex sentence: The Edwardian War was the first phase of the Hundred Years' War, lasting from 1337 to 1360, from the outbreak of hostilities until the signing of the Treaty of Brétigny.
Split into simpler sentences: The Edwardian War was the first phase of the Hundred Years'War. The first phase of the Hundred Years' War, started in 1337 and ended in 1360, with the signing of the Treaty of Brétigny.