Reengineering
Gustavus Adolphus was a very forward thinking military engineer. He reengineered the way in which his army worked, with simple innovations that proved devastating to his adversaries.
One example of this was the Swedish cavalry system. Cavalry had been pushed to the fringes of military worth and had been largely neutralized by the Spanish tercios. They were being ineffectively used to charge the enemy front or flank, fire broadsides with pistols and muskets and then retreat to reload and reform. However, Gustavus Adolphus used light cannons (reengineered to have 3 standard calibers, one of which was eventually called "The Regimental Cannon,") along with muskets to eliminate enemy pikemen, then the cavalry would swoop in and cut through enemy lines with sabers.
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