Complex sentence: On the 12 December 1776, she left India to return to Brest; at the time, France was not yet engaged in the American War of Independence, but there had been numerous incidents involving French and British ships.
Split into simpler sentences: On the 12 December 1776, she left India to return to Brest. At the time, France was not yet engaged in the American War of Independence, but there had been numerous incidents involving French and British ships.