Union of Brandenburg and Prussia

The Union of Brandenburg and Prussia, formed in 1618, was a personal union where two distinct territories—Brandenburg and Prussia—were ruled by the same monarch but remained separate states. This meant that while they had different governments and laws, they shared the same king. The union allowed the ruler to combine resources and strengthen their influence, eventually leading to the rise of Prussia as a powerful state in Europe. This arrangement lasted until Prussia became a kingdom in its own right, paving the way for future unification of German territories.