Complex sentence: It is said that John Dunn's skill at arms contributed greatly to British successes in the south, where in the north the British, anticipating Cetshwayo's refusal of the ultimatum, had already crossed the river, to be soundly beaten at the Battle of Isandlwana.
Split into simpler sentences: It is said that John Dunn's skill at arms contributed greatly to British successes in the south,. In the north the British, anticipating Cetshwayo's refusal of the ultimatum, had already crossed the river, to be suprised and soundly beaten at the Battle of Isandlwana.