Complex sentence: Peace negotiations began, and in June 842 the brothers met on an island in the Saône, and agreed to an arrangement which developed, after much difficulty and delay, into the Treaty of Verdun signed in August 843.
Split into simpler sentences: Peace negotiations began, and in June 842 the brothers met on an island in the Saône. They agreed to an arrangement which developed, after much difficulty and delay, into the Treaty of Verdun signed in August 843.