One of the most interesting changes in Proto-Germanic was the alternation of
w after short syllables with
u after long, respectively - an alternation with far-reaching effects. Described by Eduard Sievers in 1878, this «law» has been the subject of controversy ever since. Is it related to a similar phenomenon in Vedic Sanskrit, and was it, therefore, Indo-European in origin? What is its relationship to alliterative verse in Germanic? This study addresses such questions and demonstrates that Sievers' Law has played a wider role in Old English than heretofore demonstrated.