Complex sentence: Despite the fact that Charles was initially unwilling to help Edward, the French declared war on Burgundy and so Charles decided to give his aid to Edward, and from there he raised an army to win back his kingdom.
Split into simpler sentences: Despite the fact that Charles was initially unwilling to help Edward, the French declared war on Burgundy. This prompted Charles to give his aid to Edward, and from Burgundy he raised an army to win back his kingdom.