Succeeded to the throne of Prussia on 25 February 1713, he inherited the Northern War, a fight for the control of the Baltic. He quickly moved to make peace with Russia, from whom he gained Stettin in September 1713, before joining with Russia, Denmark and Britain to force Sweden out of her last footholds in Germany, gaining control of the mouth of the Oder in the process. In 1726 he joined those powers guaranteeing the Pragmatic Sanction, by which Maria Theresa was to inherit the Habsburg lands, a move his son was to repudiate dramatically. He was willing to defend Protestant rights in Germany, through threats to his own Catholics, and in 1732 gained from the oppression of the Protestants of Salzburg by offering them the option of moving to East Prussia, depopulated after a plague. His main significance was as a reformer. He reordered the civil government of Prussia, massively improving the finances of the state, but it was his military reforms that had the most lasting influence. During his reign the Prussian army increased in size from 38,000 men to 89,000, while their drill and discipline went through a revolution, producing an army that was superior to any other in Europe, something his son, Frederick the Great, benefited from in his many battles. The entire Prussian state was devoted to the support of the army (In 1740 over three quarters of the entire state revenue was spent on the army), but Frederick William never used his new army, and gained a reputation as an parade-ground general, but it was his reforms that gave Frederick the Great the means to achieve his ambitions.