Complex sentence: Lecourbe believed his forces to be insufficient for offensive action, so he decided to fall back, with a cavalry combat taking place at the Battle of Wiesloch, where d'Hautpoul's men, and Nansouty's brigade in particular, were heavily engaged.
Split into simpler sentences: Lecourbe believed his forces to be insufficient for offensive action, so he decided to fall back. During the retreat, a cavalry combat took place during the Battle of Wiesloch, where d'Hautpoul's men, and Nansouty's brigade in particular, were heavily engaged.