During the american revolution, why did many african-american slaves fight for the british and against the colonists? african-american slaves sided with the british because the colonists had excluded slave rights from the declaration of independence and the paris peace treaty. african-american slaves defected to the british after their “masters” forced them to serve in separate “black” regiments in the continental army. the british guaranteed african-american slaves that they would be liberated if they fought on the side of the british during the revolution. african-american slaves were banned from serving in the continental army across the course of the american revolution. the british assured african-american slaves passage to africa if they aided the british against the colonists.