Complex sentence: After the cessation of hostilities at the end of the American Revolution, animosity and suspicion continued between the United States and the United Kingdom, erupting in 1812 when the Americans declared war on the British.
Split into simpler sentences: After the cessation of hostilities at the end of the American Revolution, animosity and suspicion continued between the United States and the United Kingdom. This erupted in 1812 when the Americans declared war on the British.