How did the loss of unstressed syllables change Germanic languages?

The shift to a fixed stress accent on the initial (root) syllable in late Proto-Germanic had profound consequences for the development of Germanic languages, as it caused non-accented syllables to become subject to reduction and, in many cases, total loss.1

This loss of unstressed final syllables significantly impacted the grammatical structure of these languages:2

• Morphological Simplification: Because Proto-Indo-European and early Germanic languages relied heavily on final syllables to mark inflectional categories, the reduction of these syllables led to a widespread loss or simplification of case and gender systems.2
• Grammatical Shifts: As grammatical information previously carried by suffixes was lost, languages developed new ways to maintain meaning. For example, some grammatical distinctions shifted to the root vowel, such as the "i-umlaut" seen in the English foot/feet or German Fuss/Füsse alternation.1
• Verb Conjugation: While the impact on verbs was less severe than on nouns, many Germanic languages, including English, eventually lost most personal endings used to mark subjects.2

These changes illustrate how the regularization of stress fundamentally reshaped the morphology of the West Germanic languages.21