On the Germanic and Old High German distance assimilation changes

This article revisits a vexed question, namely the phonological interpretation of the Germanic and Old High German distance assimilation changes. It will be argued that 1) the prehistoric Germanic subsystem of short vowels should be reconstructed with five phonemes (/i/, /e/, /u/, /o/, /a/), not with four (/i/, /e/, /u ~ o/, /a/) or with three (/i ~ e/, /u ~ o/, /a/); 2) the Old High German umlaut phenomena produced phonemic changes before the factors that triggered them off changed or disappeared, because the umlaut allophones gradually shifted to such a degree that they became distinctive in the phonological system of the language and contrastive at a lexical level.