6. PRUSSIA´S ARMY Frederick William I and Frederick II , made Prussia a major European power in the 18 th century. In 1740, Frederick II had doubled the army`s size from the initial number of people of the beginning of the 18 th century. It had the fourth-largest army after France, Russia and Austria. The army was the most important institution in the state. Frederick was a dedicated ruler, He enlarged the Prussian army by actively recruiting the nobility into civil service.