Complex sentence: Although Daun had scored a complete surprise, he failed to follow up on his victory with a vigorous pursuit of the retreating Prussians; furthermore he allowed the entire force to escape, unite with another corps in the vicinity, and regain the momentum over the winter.
Split into simpler sentences: Although Daun had scored a complete surprise, he failed to follow up on his victory with a vigorous pursuit of the retreating Prussians. Furthermore, he allowed the entire force to escape, unite with another corps in the vicinity, and regain the momentum over the winter.