Complex sentence: As a result, the following year the Maratha Empire declared war on Sindh and Berar Subah during which Arthur Wellesley took a leading role causing much early suspicion between the Emirs of Sindh and the British Empire.
Split into simpler sentences: As a result, the following year the Maratha Empire declared war on Sindh and Berar Subah. During the war Arthur Wellesley took a leading role--causing much early suspicion between the Emirs of Sindh and the British Empire.