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How large was the Prussian army under Frederick the Great?

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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.

Under the reign of Frederick William I, the Prussian army was raised to 80,000 men, which accounted for approximately 4 percent of the population at that time. This force was composed of one-half hired foreigners and one-half subjects recruited through the "canton system," which mandated military service for young men of the lower classes.1

When Frederick II (the Great) ascended to the throne in 1740, he inherited this well-trained military machine. Throughout his reign, the size of the army fluctuated based on the demands of his military campaigns. For instance, during the Seven Years’ War, historical records indicate that Frederick commanded varying numbers of troops in specific engagements, such as 64,000 men at the Battle of Prague in 1757 and 36,000 men at the Battle of Zorndorf in 1758.123