This philosophy was a response to the increasing weight of defensive firepower that accrued to armies in the nineteenth century, as a result of several technological innovations, notably breech-loading rifled guns, machine guns, and light field artillery firing high-explosive shells. It held that the victor would be the side with the strongest will, courage, and dash (élan), and that every attack must therefore be pushed to the limit. The invention of machine guns and barbed wire as well as the subsequent development of trench warfare rendered this tactic extremely costly and usually ineffective.