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.
Who were the leaders of the two alliances?
 Great Britain on one side and France on the other.