Complex sentence: In the summer of 1636 the Cardinal-Infante reached as far as Corbie, but this city was retaken by the French in November, and at the end of the year Spain had lost most of its gains again.
Split into simpler sentences: In the Summer of 1636 the Cardinal-Infante reached as far as Corbie, but this city was retaken by the French in November. At the end of the year Spain had lost most of its gains again.