Correction: The general in charge of William of Orange army was a French protestant, Marshal Frédéric-Armand, comte de Schonberg.  There were also 100 French officers and at least 2,250 French soldiers in William of Orange's army at the Battle of the Boyne.  William of Orange expressed himself mostly in Old French and many of his letters to his confidents were written in French.  William of Orange was not anti-French, he was fighting the tyranny of the French king who was trying to impose a Catholic king on the English nation..