In the early 15th century, small "hand cannon" first began to be used, in the Hussite Wars, in combination with Wagenburg tactics, allowing infantry to defeat armored knights on the battlefield. At the same time crossbows were made more powerful to pierce armor, and the development of the Swiss Pike square formation also created substantial problems for heavy cavalry. Rather than dooming the use of body armor, the threat of small firearms intensified the use and further refinement of plate armor. There was a 150-year period in which better and more metallurgically advanced steel armor was being used, precisely because of the danger posed by the gun. Hence, guns and cavalry in plate armor were "threat and remedy" together on the battlefield for almost 400 years. By the 15th century Italian armor plates were almost always made of steel. In Southern Germany armorers began to harden their steel armor only in the late 15th century. They would continue to harden their steel for the next century because they quenched and tempered their product which allowed for the fire-gilding to be combined with tempering.