With respect to the breaching of stone masonry by siege batteries, it has long been an established principle that all masonry exposed to the fire of land batteries should be masked by earthen works. The neglect of this rule caused the fall of Bomarsund. Those who so readily draw, from the results of that siege, the inference that the present mode of fortifying land fronts must be abandoned, exhibit their ignorance of military engineering. The facts do not justify their conclusions.
With respect to sea fronts, which can be reached only by guns afloat, the case is very different. They are usually casemates of masonry, not masked by earthen works. Whether the increased efficiency of projectiles thrown by ships and floating batteries now require a resort to this mode of protecting masonry on the water fronts of fortifications, is a question well worthy of discussion. This subject has already been alluded to in the Note on Sea-coast Defences, and it is there shown that no facts have yet been developed which require or authorize any change in our present system.
As Mexico had no permanent fortifications to be besieged, the war in that country afforded very little practice in that branch of engineering which is connected with the attack and defence of permanent works, particularly sapping and mining. The only operation resembling a siege was the investment and bombardment of Vera Cruz, and it is worthy of remark that if General Scott had stormed that place, weak as it was, he must have lost a large number of his men, while from his trenches and batteries he reduced it with scarcely the sacrifice of a single life.
Nor did either party in this war make much use of field works in the attack and defence of positions. Nevertheless, no one can read the history of the war without appreciating the important influence which Fort Brown had upon General Taylor’s defence of the left bank of the Rio Grande. Again if we compare our loss in other Mexican battles with that which the Americans sustained in their attacks upon Monterey, Churubusco, Molino del Key, and Chapultepec,—places partially secured by field works—we shall be still more convinced of the value of temporary fortifications for the defence of military positions, although it was manifest that the Mexicans neither knew how to construct nor how to defend them.