The chain shift can be abstractly represented as:
Here each sound moves one position to the right to take on its new sound value.
The voiced aspirated stops may have first become voiced fricatives before hardening to the voiced unaspirated stops "b", "d", and "g" under certain conditions; however, some linguists dispute this. See Proto-Germanic phonology.
Grimm's law was the first non-trivial systematic sound change to be discovered in linguistics; its formulation was a turning point in the development of linguistics, enabling the introduction of a rigorous methodology to historical linguistic research. The "law" was discovered by Friedrich von Schlegel in 1806 and Rasmus Christian Rask in 1818. It was elaborated (i.e. extended to include standard German) in 1822 by Jacob Grimm, the elder of the Brothers Grimm, in his book Deutsche Grammatik.
Further changes following Grimm's Law, as well as sound changes in other Indo-European languages, can sometimes obscure its effects. The most illustrative examples are used here.
Note: Proto-Germanic *gw from Proto-Indo-European *gʷʰ has undergone further changes of various sorts. After *n it was preserved as *gw, but later changed to *g except in Gothic. Elsewhere, it became either *w or *g during late Proto-Germanic.
This is