Complex sentence: On December 4,1838 the Patriots crossed the Detroit River into Canada by steamboat and engaged in an unsuccessful battle at Windsor where the Patriots set the British barracks on fire, burn the steamer "Thames" and several houses, and killed four militiamen before retreating.
Split into simpler sentences: On December 4,1838 the Patriots crossed the Detroit River into Canada by steamboat and engaged in an unsuccessful battle at Windsor. Where the Patriots set the British barracks on fire, burn the steamer Thames and several houses, and killed four militiamen before retreating.