Prussia (Königreich Preußen/Preussen) was a German state that existed from 1525 to 1947 in various forms. It was primarily located in what is today Eastern Germany, Poland, Russia's Kaliningrad Oblast exclave, and small parts of Lithuania and Czechia.
(left) State Flag of the Kingdom of Prussia (1892-1918); (right) greater Prussian coat of arms (1866-1918)
History
The first mention of the name "Prussia" comes from the high Middle Ages, referring to a Baltic Tribe that lived in the area that is today the Kaliningrad Oblast of Russia. They unsuccessfully revolted against the Teutonic Knights, German crusaders sent to Christianise the pagan tribes of the Baltic regions in the 13th century. For several centuries the region remained under the rule of the Teutonic Knights, until in 1525 when the Knights' Grand Master Albert of Brandenburg-Ansbach secularised his lands as the Duchy of Prussia in the wake of the Protestant Reformation. The little Duchy then, in 1618 entered into a personal union with the Margraviate of Brandenburg, and it saw involvement in various European wars of the 16th and 17th centuries, such as the Thirty Years War (1618-48) where it switched sides three times.
Brandenburg-Prussia (red) within the Holy Roman Empire (yellow); note how Brandenburg is within the HRE, and physically separated from Prussia, which is outside the HRE. Yet they shared the same monarch (a personal union) from 1618 to 1701, like Hanover and Great Britain from 1714 to 1837.
The second half of the 17th century saw the potential for Brandenburg-Prussia to become a local power as it centralised under elector Friedrich Wilhelm, allowing it to establish a standing army that won several major victories. The state's population grew with its policy of accepting Protestant refugees from other parts of Europe; it even had some short-lived colonies on the West African coast. In 1701 the part of Prussia, being outside the Holy Roman Empire was elevated to a Kingdom, integrating within it the HRE state (and the other Hohenzollern dominion) of Brandenburg. From then on both patches of land ruled by the Hohenzollerns were referred to as simply "Prussia". Military victories in the Great Northern War (1700-21) against Sweden expanded its territory and power; but it took a defeat of Hapsburg Austria in the War of Austrian Succession (1740-48) and acquisition of Silesia for the ascendant kingdom to be considered a great power. However, in 1756 another war with Austria (the Seven Years War) began over Saxony. Despite being heavily outnumbered on the continent, against France and Russia, King Friedrich II "The Great" demonstrated his military skills and avoided defeat until Russia left the war (when a protégé of his, Peter III became Tsar). The Treaty of Paris that ended the Seven Years War in 1763 further highlighted Prussia's newfound status in Europe, bankrupting France and humiliating Habsburg Austria. Prussia was also able to physically unite its territories with its acquisitions in the First, Second and Third Partitions of Poland (1772, 1791 and 1795), which ended the Polish-Lithuanian Commonwealth.
Prussia in 1800; Green is for territories acquired in the 1st Polish Partition (1772) and Blue in the 3rd (1795).
Throughout this rise to power, Prussia had remained an absolute monarchy under the Hohenzollerns, who were alarmed when the French Revolution erupted in 1789. After Louis XVI of France was deposed by the National Assembly in 1792, Prussia, along with many other conservative monarchies in Europe, declared war on the new French Republic. The Prussian army, with its new formidable reputation gained over the last century of wars, was however defeated at Valmy, and by 1795 a peace had been signed. However, following the rise of Napoleon, the establishment of his French Empire (1804) and his sound military defeat of the Austrian Empire at Austerlitz (1805), Prussia, fearing more French expansion declared war on France with British and Russian support the following year. Friedrich Wilhelm III, Prussia's new king was less militarily gifted than his famous predecessor, and thus Prussia was quickly crushed at the battles of Iéna and Auerstadt (1806). The 1807 Treaties of Tilsit stripped Prussia of much of its recently gained land, re-establishing a Polish state called the Duchy of Warsaw, a French satellite.
French troops entering Berlin, during the War of the Fourth Coalition (1806-07). This war also resulted in Napoleon's dissolution of the millennium old Holy Roman Empire, reorganising it into the friendly Confederation of the Rhine.
Following its defeat by Napoleonic France, Prussia engaged in military and administrative reforms, but was forced to join Napoleon's Continental System and became subjugated to a France that dominated Europe up to the Vistula. It contributed troops to Napoleon's disastrous 1812 invasion of Russia; but when it became clear that the Grande Armée had been beaten, Prussia (and other German states similarly subjugated by Napoleon, like Austria and Saxony) promptly switched sides and declared war on France in the War of the Sixth Coalition (1812-14). Napoleon was defeated at the Battle of Leipzig (1813), and by May 1814, Prussian horses were "being watered in the Seine". Napoleon abdicated to Elba after the Coalition entered Paris, and the Congress of Vienna opened to negotiate the post-war world. However, Napoleon's escape triggered the War of the Seventh Coalition (1815), a short-lived campaign which ultimately saw his final defeat by British, Dutch and Prussian forces at Waterloo.
Meeting of Tsar Alexander I of Russia, Emperor Franz I of Austria and King Friedrich Wilhelm III of Prussia after Napoleon's defeat at Leipzig, 1813.
The Congress of Vienna redrew the boundaries of Europe after the Napoleonic Wars, establishing a new German Confederation of 39 states to replace the HRE. Prussia and Austria, the two strongest states in the Confederation, shared influence amongst the smaller states; with Prussia annexing large sections of the Rhineland to its territory; and as time went by, Prussia established links with the smaller states, such as the Zollverein in 1834, a customs union amongst the German states, and a series of road, rail and canal links that increased trade and commerce in the region. The early-mid 19th century was a time of increasing liberalism and nationalism, seeds sown by Napoleon's wars, and the absolutist, reactionary Prussian monarchy rejected most liberal reforms. When the Revolutions of 1848 (the "Springtime of Nations") broke out, the Frankfurt parliament offered the new king Friedrich Wilhelm IV the crown of a unified Germany, but he refused this "crown from the gutter" on the grounds that a liberal constitution was unacceptable to the princes of the smaller states.
The German Confederation after the Congress of Vienna in 1815; note how both Austria and Prussia own additional territories outside the boundaries of the Confederation. Prussia became a constitutional monarchy after the 1848 revolutions.
Nevertheless, as German nationalism grew, in 1849 Prussia and Austria took action against Denmark when it attempted to control the German duchies of Schleswig and Holstein. This war was inconclusive, but fanned the flames of idealist pan-German activists across the Confederation. With the appointment of Otto von Bismarck by newly crowned King Wilhelm I in 1862, German unification accelerated with a solution to the "Danish question" being found with Prussian-Austrian intervention against Denmark in 1864, this time successful. The Austrians contested the end arrangements in Schleswig-Holstein a few years later, providing a casus-belli against them and their allies. This war, known as the Austro-Prussian War (1866) saw the Austrians soundly defeated at Königgratz, with the end result being the end of the 1815 Confederation and Prussian hegemony over the German states that had allied with Austria in the war (Hanover, Bavaria, Württemberg, Baden, etc.), and the following year Prussia formed a new "North German Confederation", annexing many of the smaller German states that year.
Prussia (or the North German Confederation; Norddeutscher Bund) at its largest pre-unification extent in 1866-71.
This war had effectively tipped the balance of power in Europe, and Austria was now relegated to a minor power; no longer did it have any influence in Germany, and now it reformed into a dual-monarchy (Austria-Hungary; Österreich-Ungarn) and looked to expand in the Balkans instead. France's Napoleon III was drawn into confrontation with Prussia; in 1867 war nearly broke out over Luxembourg. Tensions rose further when a Prussian prince was offered the Spanish throne, but was pressured by France to turn it down. Finally, in 1870, Bismarck provoked France into declaring war by editing the "Ems Telegram" to be much more offensive and then publicising it. The southern German states (Hesse, Bavaria, Baden and Württemberg) joined the war; with the Germans' industrial capability, railway network and military reforms under Helmuth von Moltke, French forces were defeated at the Battle of Sedan, and Napoleon III himself captured. The Prussian army would go on to besiege Paris, until the new French Third Republic signed the Treaty of Frankfurt the following year; the German princes gathered in the Palace of Versailles on the 18th of May 1871 to proclaim the unification of the German Empire; known also as "Kleindeutschland"; a unified Germany excluding German-speaking Austria.
The 1871 Proclamation of the German Empire in the Palace of Versailles as depicted by Anton von Werner (painted 1884).
Following German unification, the Kingdom of Prussia continued to exist within the German Empire as its largest component; with 2/3rds of its land and 3/5ths of its population. The Prussian king also inherited the office of the Emperor (Kaiser) of Germany, and although 24 other German states continued to exist within the new Germany in their pre-unification forms, they answered undisputedly to Berlin, the capital of the new country, an industrial and military giant of the time. Wilhelm I "the Great" died in 1888, and was succeeded by his son Friedrich III, who died in 90 days; thus his own son Wilhelm II became King of Prussia until the German revolutions of 1918 overthrew the monarchies of the German Empire right before the armistice that ended WWI. During the Weimar Republic Prussia remained a "state" in Germany, as the "Free State of Prussia" (Freistaat Preußen); when the NSDAP came to power in 1933, the administrative entity of Prussia effectively ceased to exist and it was divided into Gaue. Prussia was finally dissolved in 1947 by the Allies after the end of WWII, and its territory was divided between West Germany, East Germany, Poland and the USSR.
A more detailed account of post-unification Germany's history can be found here.
Coinage*
The Duchy of Prussia issued coinage in the 16th century; but certainly after entering into personal union with Brandenburg in 1618 it saw circulation of coins minted in Brandenburg, which commonly depicted the Brandenburg eagle and an orb motif. Both coinage systems mentioned above were Reichsthaler-based; from 1750 the "Prussian thaler" was distinct from the Reichsthaler (1/12th a Cologne Mark), as it now had subdivisions of 288 pfennige, or 24 groschen making a thaler (1/14th a Cologne Mark); later on, from 1821, when Prussia's coinage became unified (regions such as Poland had their own coinages for some time) it became 360 pfennige , or 30 [Silber]groschen making a thaler.
Examples of the Prussian thaler worth 1/14th of a Cologne Mark
The Vereinsthaler was introduced in 1857 as a standard monetary unit in the German Confederation, allowing for ease when travelling and establishing a currency union (one was introduced earlier in 1837). From the 1830's to the 1870's, German states issued Vereinsthaler-based coinage; Austria stopped after 1867. The new decimal currency adopted by the German Empire in 1871 was at the rate of 3 mark to a Vereinsthaler, with 10 pfennige coins becoming equivalent to 1 groschen. Thus the pre-decimal coins' names became common nicknames for their post-decimal equivalents, a habit that has persisted until the adoption of the Euro in 2001 by Germany in some older people.
Examples of Vereinsthalers issued by Prussia; these became standard dimensions throughout the German Confederation.
Following German unification, Prussia and some of the other kingdoms, grand duchies, duchies and Free Hanseatic cities within the German Empire continued to mint their own higher-denomination coinage; with decimal issues replacing the last thalers in the mid 1870's. Lower denomination coins, from 1 pfennig to 1 Mark, were ubiquitous without any state-by state variation (other than mintmark); while coins from 2 to 20 Mark usually featured common reverses of the German eagle; and state-specific obverses (usually the state's monarch). Some commemoratives, such as those issued in 1913 for the centennial of the declaration of war against Napoleon by Prussia, deviate from this common trend. After the end of the German monarchies in 1918, German states stopped issuing their own high-denomination coins at all, although the states themselves continued to exist in administrative capacity until 1933 (de facto) and 1947 (de jure).
Examples of the common obverses of high-denomination German Empire coins; the eagle on the left was used until 1890, and the one on the right until 1918.
Duchy of Prussia:
https://en.numista.com/catalogue/etats_allemands-39.html#devise4563
Brandenburg-Prussia:
https://en.numista.com/catalogue/etats_allemands-9.html#devise6157
Kingdom of Prussia (pre-unification, Prussian thaler):
https://en.numista.com/catalogue/etats_allemands-39.html#devise436
Kingdom of Prussia (pre-unification, Vereinsthaler):
https://en.numista.com/catalogue/etats_allemands-40.html#devise2025
Kingdom of Prussia (post-unification, Mark):
https://en.numista.com/catalogue/etats_allemands-41.html#devise661
*Seriously, this was extremely complicated. I'm still not sure if I've got it right. I don't think I'll do another German state for some time.