Why did Frederick the Great oppose Joseph II’s plan to acquire Bavaria?

Frederick the Great of Prussia opposed Joseph II’s attempts to acquire Bavaria primarily because he sought to prevent any increase in the strength of the Habsburgs and maintain the balance of power in central Europe.12

Frederick’s opposition manifested in two major instances:

• The War of the Bavarian Succession (1778–1779): After the Bavarian electoral line failed, Joseph II reached an agreement to cede parts of Bavaria to Austria. Frederick declared war to frustrate this expansion, leading to a conflict largely characterized by maneuvering rather than major battles, known as the "Potato War." The resulting Treaty of Teschen forced Austria to abandon most of its claims.312
• The Exchange Plan (1785): Joseph II later proposed an ambitious exchange of the Austrian Netherlands for all of Bavaria. Frederick again opposed this, viewing it as a threat to the regional balance of power. He successfully formed the Fürstenbund (League of Princes), a coalition of German rulers pledged to defend the empire's fundamental laws, which ultimately persuaded Joseph to drop the plan.12

Throughout these events, Frederick acted to preserve a decentralized German political structure that favored his own dynastic interests over Habsburg hegemony.12