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What did the Peace of Oliva of 1660 mean for Prussia?

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Historical map showing the unification of Germany by Prussia in the late 19th century. The map highlights in green the Kingdom of Prussia as of 1866, and in yellow the additional territories that formed the German Empire by 1871-1918, encompassing most of north-central Europe. Neighboring countries such as France, Belgium, the Netherlands, Denmark, Sweden, Russia, Austria-Hungary, and Switzerland are labeled, with major regions and states within the empire clearly marked. — Prussia The unification of Germany by Prussia, which brought most of north-central Europe into one kingdom.

The Treaty of Oliva (1660), which concluded the First Northern War, was a pivotal moment for Prussia. While the treaty primarily restored the territorial status quo between Sweden and the Polish-Lithuanian Commonwealth, it served to formally confirm the full sovereignty of the Hohenzollern elector Frederick William over the Duchy of Prussia.123

Prior to this, the duchy had been held as a Polish fief. Frederick William had previously secured the renunciation of Polish suzerainty through the Treaty of Wehlau in 1657, and the Treaty of Oliva ratified this status. By ending Poland's overlordship, the treaty allowed the Hohenzollerns to become sovereign rulers of Ducal Prussia, distinguishing it from their other territories that remained nominally part of the Holy Roman Empire. This transition was fundamental to the rise of the Hohenzollern monarchy as a great power in Europe.143