William Congreve noticed the Indian use of rockets, decided to explore their possibilities ( though he seems later to have tried to downplay the extent of Indian influences ). He was able to demonstrate how devastating an explosive -tipped rocket could be and compared their light weight to that of the equivalent artillery pieces, especially siege mortars. The rocket carcass is not only fired without re-action upon the point from which it is discharged, but is also unencumbered with the necessity of heavy ordnance to project it, as is the case with every other carcass. These are the points which first induced me to speculate upon it. … It is ammunition without ordnance, it is the soul of artillery without the body. (quote from the second article) Some were used in the Napoleonic Wars, and in the War of 1812. The "rockets' red-glare" in the US national anthem refers to his rockets. The problem came with precise aiming of them; it was easier to predict where a shell would land than where a rocket would hit.