Since PIE left no written records, historical linguists construct family trees, an idea pioneered by August Schleicher, on the basis of the comparative method.The comparative method takes shared features among languages and uses procedures to establish their common ancestry.The common origin of European languages and Sanskrit was first proposed by Sir William Jones(1746-1794).Systematic comparisons between these languages by Franz Bopp supported this theory and laid the foundation for postulating that all Indo-European languages descended from a common ancestor, Proto-Indo-European (PIE), thought to have been spoken before 3,000 B. It then split into different branches which, in turn, split into different languages in the subsequent millennia.First Germanic Sound Shift (Grimm’s Law) You probably know of Jacob Grimm as the author of fairy tales.But he was also one of the great linguists of the 19th century.The trope often takes the form of An Aesop along the lines of "he won the battle but lost the war" (or the other way around). Also, compare Hollywood Tactics which shows unrealistic battle plans that, logically, should fail but don't. Strategy itself is often dealt with by The Strategist who may or may not also be proficient in tactical thinking.
They were once spread over Europe in the pre-Christian era.
It is not the only method available but is one that has been most widely used.
The examples below show how this method actually works with some Indo-European languages.
As a result, the reconstruction of PIE phonology continues to be a matter of scholarly debate and speculation.
Among the most notable reconstructions are those by August Schleicher, Karl Brugmann, Winfred Lehmann, Oswald Szemerènyi, and Jacob Grimm.