Seven Years' War
The Seven Years' War (1756 - 1763) was an international conflict involving Prussia against the allied European nations. It was caused by the tension between Austria and Prussia as well as Great Britain and France. Great Britain, allied with Prussia, Hanover Portugal and other European minor countries, waged war upon France, Spain, Austria, Russia and other minor European countries, leading to what has been referred to as the 'First World War', although in modern terms that would be WWI. War broke out in 1754 in Europe and later spread to North America, Scandinavia and India. It resulted in France losing much of it's claim on New France, Spain losing Florida and Bengal while receiving Louisiana from a defeated French.
In the Diplomatic Revolution of 1756, the French, Austrians and Russians made an alliance against Prussia, resulting in assistance from Great Britain, who saw Hanover, threatened by France's militaristic style. The British hoped that these alliances would bring peace to Europe, but instead this was one of the major causes.
Course of the war
Although British Prime Minister, the Duke of Newcastle, remained optimistic that war wouldn't break out, the French attacked Minorca in April, sparking the war. A British attempt at relieving Minorca failed, and Minorca fell on 28 June. War was later declared war on 18 May, nearly two years after the Seven Years' War was believed to have started.
Having received reports of clashes in North America, and with the backing of an Anglo-Prussian Alliance, Frederick I crossed the border at Saxony on 29 August. Saxony was one of rival Austria's allies; he intended this as a pre-emption of an anticipated Austro-French invasion of Silesia.