The Seven Years' War was fought between 1755 and 1764, the main conflict occurring in the seven-year period from 1756 to 1763. It involved every great power of the time except the Ottoman Empire, and affected Europe, the Americas, West Africa, India, and the Philippines. Considered a prelude to the two world wars and the greatest European war since the Thirty Years War of the 17th century, it once again split Europe into two coalitions, led by Great Britain on one side and France on the other. For the first time, aiming to curtail Britain and Prussia's ever-growing might, France formed a grand coalition of its own, which ended with failure as Britain rose as the world's predominant power, altering the European balance of power. 

Realizing that war was imminent, Prussia preemptively struck Saxony and quickly overran it. The result caused uproar across Europe. Because of Prussia's alliance with Britain, Austria formed an alliance with France, seeing an opportunity to recapture Silesia, which had been lost in a previous war. Reluctantly, by following the imperial diet, most of the states of the empire joined Austria's cause. The Anglo-Prussian alliance was joined by smaller German states (especially Hanover). Sweden, fearing Prussia's expansionist tendencies, went to war in 1757 to protect its Baltic dominions, seeing its chance when virtually all of Europe opposed Prussia. Spain, bound by the Pacte de Famille, intervened on behalf of France and together they launched an utterly unsuccessful invasion of Portugal in 1762. The Russian Empire was originally aligned with Austria, fearing Prussia's ambition on the Polish-Lithuanian Commonwealth, but switched sides upon the succession of Tsar Peter III in 1762.
How long did the Seven Years' War last?
When did it start?
When did it end?
Why was it called the Seven Years' War?
Who were the leaders of the two alliances?
Who came out ahead?
Who fired the first shot?
Who did most of the Holy Roman Empire join?
Who did Russia join?
Who attacked Portugal?
Who won?
Which major European power stayed neutral?
What was this war a prequel of?
Why did Austria join?
Which state was the first to be defeated?
What was India's role?
What ruler's rise changed the balance of power significantly?
Whom did Prussia have its eye on?
Nine years
The Seven Years' War was fought between 1755 and 1764
1755
The Seven Years' War was fought between 175
1764
The Seven Years' War was fought between 1755 and 1764
Because the main part of the conflict happened from 1756-1763.
the main conflict occurring in the seven-year period from 1756 to 1763
Great Britain and France
 Great Britain on one side and France on the other.
Great Britain
France formed a grand coalition of its own, which ended with failure as Britain rose as the world's predominant power
Prussia
Realizing that war was imminent, Prussia preemptively struck Saxony and quickly overran it.
France
 Austria formed an alliance with France, seeing an opportunity to recapture Silesia, which had been lost in a previous war. Reluctantly, by following the imperial diet, most of the states of the empire joined Austria's cause.
Both
The Russian Empire was originally aligned with Austria, fearing Prussia's ambition on the Polish-Lithuanian Commonwealth, but switched sides upon the succession of Tsar Peter III in 1762.
Spain and France
 Spain, bound by the Pacte de Famille, intervened on behalf of France and together they launched an utterly unsuccessful invasion of Portugal in 1762.
Portugal
utterly unsuccessful invasion of Portugal 
Ottoman Empire
 except the Ottoman Empire
The World Wars
Considered a prelude to the two world wars
To recapture Silesia.
 Austria formed an alliance with France, seeing an opportunity to recapture Silesia
Saxony
 Prussia preemptively struck Saxony and quickly overran it.
unknown
unknown
Tsar Peter III
but switched sides upon the succession of Tsar Peter III in 1762.
The Polish-Lithuanian Commonwealth
fearing Prussia's ambition on the Polish-Lithuanian Commonwealth,