The Seven Years War was fought from 1756 to 1762. It was a pivotal moment in European history, establishing the kingdom of Prussia as one of the major powers of Europe, and paving the way for Prussia's unification of Germany in the 19th century.
In the 18th century, Germany was a loosely confederated collection of kingdoms and prinicpalities, under the ostensible control of the Holy Roman Empire. Indeed, all of Europe was a complicated patchwork of shifting alliances and dynasties, with national boundaries often less important than the holdings of a particular ruling house.
The kingdom of Prussia, formed in 1701, consisted of a number of non-contiguous territories, ruled by the Hohenzollerns, who had been electors of Brandenburg since the 15th century. The state of Brandenburg, in northeastern Germany, formed the core of Prussia, with East Prussia, in modern-day Poland the next largest part of the country. Prussia also included part of Pomerania to the north, and various smaller holdings throughout Germany.
Frederick II became king of Prussia at his father's death in 1740. Shortly after taking the throne, he had taken the territory of Silesia from the larger and more powerful kingdom of Austria, during the War of Austrian Succesion.
Queen Maria Theresa of Austria, who had not yet given up hope of regaining Silesia, was one of the main instigators of the Seven Years War. The other was Czarina Elizabeth of Russia, who had a strong animosity for Frederick, allegedly stemming from his having publicly made fun of her in front of his court.
Thus, in 1755, Russia and Austria signed a treaty agreeing to conquer Prussia and divide it between them. Saxony and Sweden were also involved in the alliance. Saxony lay immediately to Prussia's south, west of Silesia, and Sweden controlled part of Pomerania, which adjoined Prussia to the north. Both were promised pieces of Prussia by the treaty.
Frederick learned of this alliance, and in January 1756, he signed an alliance with England. The English king, George II, was also the Elector of Hanover, and so had a strong interest in Germany. This led France to join the Austria-Russian alliance in May 1756.
For France and England, the war was one for colonial domination of North America and India. Their conflict, simultaneous with the Seven Years War, is known in the U.S. as the French and Indian War. (Americentric Disclaimer -- I'm not sure how this war is called elsewhere.) England's military involvement on the continent was limited to a small army defending Hanover, but they gave Prussia an annual monetary subsidy which proved essential to Frederick's ability to sustain the war effort.
Prussia was now threatened by four major powers, whose populations and armies vastly outnumbered its own. Frederick had few advantages to call on. The first was preparation. His father and grandfather had built one of the finest militaries in the world, and Frederick had improved it until the Prussian army was second to none. His position was also an advantage, though it seems paradoxical to say so. Being surrounded meant he could use internal lines of communication to move his troops where they were needed, while his enemies were far from each other and had difficulty co-ordinating their efforts.
However, Prussia's greatest advantage lay in the fact that Frederick was quite simply one of the most brilliant generals in history. By 1755, at age 43, he was already known as Frederick the Great, having earned respect throughout Europe for his victory in the War of Austrian Succession. An astute political observer, he had spent the ten years since then expecting and planning for the conflict he now faced.
Frederick's military philosophy was firmly based on the principle of offense. Thus, hoping to quickly eliminate one of the coalition before they gathered troops and organized, he attacked. After setting troops to defend each front, he invaded Saxony on August 28, 1756.
He planned to roll through Saxony and to take Vienna, but his conquest of Saxony took longer than he had hoped. Forced to halt his advance as winter approached, he took advantage of the delay to consolidate his hold on Saxony, incorporating its army into his own.
In the spring of 1757, he pushed into Bohemia, which lies to the south of Saxony and was then part of Austria. On May 6 he defeated an Austrian army and laid siege to Prague. However, the siege was broken on June 18, and Frederick was forced to return to Saxony.
Meanwhile, the allied forces were gathering. The Russians invaded East Prussia, while the Swedes advanced into Pomerania. The French, along with a contigent assembled by a number of smaller German states advanced into Hanover. The English commander in Hanover, the Duke of Cumberland, King George's brother, was defeated by the French on July 26 and returned to England, forcing the Prussian troops defending Hanover to retreat into Brandenburg.
The Russians defeated the Prussian force in East Prussia on August 30, and soon occupied all of East Prussia.
Frederick dashed from one front to another, with the opposing armies often retreating in front of him despite numerical superiority. On November 5, he brought the French-German force to battle at the village of Rossbach in western Saxony. Outnumbered nearly 3 to 1, he defeated them decisively.
The Austrians, however, had by this time taken most of Silesia. Frederick made a forced march back to Silesia, and faced the Austrians at the village of Leuthen on December 5. Again he was outnumbered, by more than 2 to 1, and again he won decisively.
Early in 1758, with Russia and Sweden bogged down in snow and mud, Frederick moved against Austria. He hoped to leave them unable to threaten his rear when he turned to face the Russians later in the year. After moderate success, he was forced to respond when the Russians began to advance on Brandenburg.
The Russians had besieged Prussian defenders near Frankfort on the Oder river, east of Berlin. On August 25, in a brutal battle which left nearly half of each army dead or wounded, Frederick defeated the Russians, ending their immediate threat.
Austria meanwhile moved into Saxony, and Frederick rushed back with a small army. The Austrians withdrew at word of his approach. In the next two months, despite losing a battle where he was caught by surprise and forced to retreat, Frederick chased the Austrians out of both Silesia and Saxony.
By the end of 1758, Frederick had regained all his territory except East Prussia, including Saxony. A combined Prussian and English force was well established in Hanover. His stunning victories had made his enemies afraid to face him in battle. Yet he had lost over 100,000 troops, out of the 150,000 he had at the start of the war. While his armies still numbered nearly 150,000, they were largely new recruits, not the finely trained soldiers he'd once had.
In 1759, the forces in Hanover battled the French, with no major gains by either side. Frederick again had to defend his eastern front at the Oder river, this time against a combined Russian and Austrian force. On August 12 he suffered the worst defeat of his career, losing over 20,000 men, his army retreating in disorder for the first time ever. Had the enemy pushed on to Berlin, the war was won. But they hesitated, Frederick regrouped, reinforcements arrived from Hanover, and Frederick managed to hold out until, running out of food, the Russians withdrew to Poland.
In 1760, despite a co-ordinated plan by the allies, and their continuing numerical advantage, Frederick fought them off once more, with no real gain or loss of territory.
Early in 1761, however, Frederick's situation was dire. He had but 96,000 men. King George II had died and, more importantly, British Prime Minister William Pitt was voted out of office, and the new prime minister, determined to end the war, was planning to cut off the monetary support on which Frederick relied to pay his troops.
Frederick managed to hold out through 1761, successfully maneuvering throughout the summer to keep the Austrians and Russians from joining forces in Silesia. By the end of the year, however, his situation was desperate. He had lost Saxony and most of Silesia, along with most of Pomerania. East Prussia was still occupied. England did cut off his support, and his army was down to 60,000 men.
In the end, it was luck that saved Prussia. Czarina Elizabeth of Russia died on January 5, 1762. Her nephew, Peter III took the throne. A great admirer of Frederick, and of all things Prussian, Peter immediately made peace, returning East Prussia. Indeed, he sent 20,000 men to help Prussia against Austria. The peace was formalized May 15 in the Treaty of St. Petersburg. Sweden followed suit, making peace with Prussia in the Treaty of Hamburg on May 22. When the Prussian and British forces in Hanover routed the French on June 24, the war was all but won, with only Austria still to deal with.
When Peter's wife Catherine (later known as Catherine the Great) seized the throne in early July, she recalled the troops Peter had sent to Prussia. Nonetheless, Frederick quickly drove back the Austrians, and Maria Theresa offered to make peace. An armistice in November was followed by a peace treaty between Austria, Saxony, and Prussia in February 1763. At the same time, France and England signed the Treaty of Paris, in which England gained control of North America and India.
Prussia retained possession of Silesia and, more importantly, survived, having established itself as one of the great powers of Europe.
Much of the information in this write-up can be found in The Military Life of Frederick the Great by Trevor DuPuy.