All military historians speak of the influence of fortifications in the Peninsular campaigns:  those which had been given up to Napoleon previous to the opening of hostilities, contributed very much to the success of his arms, while those which were retained by Spain and her allies, contributed in an equal degree to hamper and embarrass his operations.  Some of these, like Saragossa and Tarragona, with their broken walls and defective armaments, kept the enemy in check some sixty days each, and did much to weaken the French power in the Peninsula.

Temporary or field-fortifications also had an important influence here.  The lines of Torres-Vedras, the field-works of Ronda, the intrenched camps of the Pyrenees, Bayonne, Toulouse, &c., are examples under this head.  In fact, field-works played a most important part in all of Napoleon’s wars.  We might mention the redoubt of Montenotte, the intrenchments at Milesimo, the batteries of Lobau, the field-defences of Hougomont, La Haye-Sainte, and Papelotte at Waterloo, and numerous other cases equally striking.  Just before the battle of Waterloo, Wellington employed some eighteen thousand peasants and two thousand horses, under the direction of British officers of engineers.  In speaking of these defences, Colonel Pasley says:  “It may be easily conceived that to have directed such a great body of workmen to proper advantage, by means of a few officers of engineers, would have been impossible, but for the system adopted of subdividing the various works among the non-commissioned officers and privates of the engineer troops, each of whom was made responsible for laying out the details of his own portion, and for the direction of a party of from twenty to one hundred men, or even more, according to circumstances.”

But to return to the Peninsular war.  These campaigns exhibit in strong colors the advantages derived, on the one side, from a well-organized engineer corps, and the losses, delays, and defects suffered on the other, until the defects of the organization were remedied.  Napoleon entered Spain with a well-appointed army, and soon, through strategy and well-directed force, gained possession of the important fortresses of the Peninsula; seizing in this way the strategic routes and important geographical points, he was enabled to retain possession of the country for eight years, in spite of the numerous forces arrayed against him, the absence of himself and his best generals in Germany, and the great inefficiency of Joseph and of many of his generals.  These fortifications were old, and of strength inferior to modern works of defence, but it required years and the expenditure of millions in blood and treasure to expel from the country those who had possession of them.