Complex sentence: The relative calm of this period was shattered during his second year as governor of the colony, when King Philip's War erupted in June 1675, becoming the most catastrophic event in Rhode Island's colonial history.
Split into simpler sentences: The relative calm of this period was shattered during his second year as governor of the colony, when the King Philip's War erupted in June 1675. It became the most catastrophic event in Rhode Island's colonial history.