 One notable exception to Napoleon's "strategy of annihilation" and a precursor to trench warfare were the Lines of Torres Vedras during the Peninsular War.French Armies lived off the land and when they were confronted by a line of fortifications which they could not out flank, they were unable to continue the advance and were forced to retreat once they had consumed all the provisions of the region in front of the lines.The Peninsular campaign was notable for the development of another method of warfare which went largely unnoticed at the time, but would become far more common in the 20th century.