A two-wheeled wagon, the caisson carries ammunition; hitched to a second caisson, it can help carry pontoon boats that will form the foundation for the bridge the French want to float across the Tagus river. (See “Pontoon Boat,” below.)

A company of soldiers in Napoleon’s army contains roughly 140 soldiers. (By long tradition, this number is similar in most nations’ armies then and now.) Sergeant Godinot and his squad serve in one of the six companies that march upriver along the Tagus, where, in Chapters 9 and 10, they skirmish in the hills with Dodd’s group of Portuguese irregulars. Godinot’s company, when on the march, walks at the back as the rear guard of its regiment.

A dragoon is a mounted infantryman who uses a horse to reach a field of battle quickly—surprising the enemy, moving quickly to a weak spot on the front—but then usually dismounts and fights on foot. Dragoons sometimes fight from the saddle, depending on the situation; in that respect, they are similar to cavalrymen, whose main purpose is to attack while mounted.