The Seven Years' War (1756–1763) was, amongst other things, a struggle for Imperial dominance in North America and South Asia at the end of which the British gained the upper hand in those territories and when in particular they gained superiority over maritime trade routes.

This had a significant impact on the spread of English in the following century as anglophone missionaries spread out from anglophone colonial possessions - at least when they were allowed to by local governors and administrators.

British influence also advanced in two other ways - one was the Scottish Enlightenment of the later 18th and early 19th Century.

The writers of associated with that movement, especially David Hume (1711-1776) and Adam Smith (1723-1790), who were best friends throughout their life incidentally, had a particular impact on German thinkers, Immanuel Kant (1724-1804) and the later Karl Marx (1818-1883) especially wrote in reaction to these thinkers.

More significantly was the industrialisation taking place throughout the 19th century that was to be emulated by other countries of Europe and elsewhere.

Another factor was the French Revolution and subsequent Napoleonic Wars (1789-1815). The Revolution made France something of a pariah state in many countries and the subsequent Napoleonic dominance of Europe had, for different reasons, a similar impact.

However the real shift of English into premier position as a world language of communication was, probably unsurprisingly, came at the end of World War II and United States foreign policy after 1945 in Europe and around the world.

And this has remained pretty much the case into the present.

Even today, around 95% of all scientific research is published in English and that looks unlikely to change in the near future, even with the rapid development of ever more effective machine translation and even interpreting apps.

We're probably less than 20 years away from the development of an app that can effectively live interpret speech with a high degree of accuracy between languages as different as Swedish and Japanese.

I can suggest some reading that might interest you on this if you like.