During the 1600's, the Hohenzollern family began to expand its power in eastern Germany. The Hohenzollerns ruled the state of Brandenburg. Berlin was their capital. In 1618, the ruler of Brandenburg inherited the duchy of Prussia. The Peace of Westphalia added part of Pomerania and some territories on the lower Rhine River to the Hohenzollern holdings.

The Hohenzollerns' rise to power began with Frederick William (the Great Elector), who became ruler of Brandenburg in 1640. He began to unite and expand his lands after the Thirty Years' War. In 1701, his son Frederick became the first king of Prussia. The Hohenzollerns' power continued to grow under the next two kings, Frederick William I and Frederick II (the Great).

The Hohenzollerns built a large, well-trained professional army and a strong civil service to defend and rule their scattered territories. Through their civil service, they improved farming and industry, and filled their treasury with tax money. They built canals, schools, and roads, and promoted the arts and learning.

After Frederick the Great became king in 1740, he seized Silesia, a rich province of Austria. This invasion led to fighting between Prussia and Austria in two wars, the War of the Austrian Succession (1740-1748) and the Seven Years' War (1756-1763). Many other nations fought in these wars. Some sided with Frederick, and others with his enemy, Empress Maria Theresa of Austria. Under the final peace treaty, Silesia remained under Prussian rule. Prussia was now recognized as a great power.

During the 1770's, Prussia, along with Austria and Russia, began to seize parts of Poland. By the end of 1795, Poland had been divided among these states.