Complex sentence: During the winter, the French prepared for a new campaign in spring 1863, while in Puebla, Mexican forces under the command of General Ortega built new fortifications, including "Fuerte" ("fort") San Javier.
Split into simpler sentences: During the winter, the French preparing for a new campaign in spring 1863. In Puebla, Mexican forces under the command of General Ortega built new fortifications, including "Fuerte" ("fort") San Javier.