In consequence of the familiar High German consonant shift, the voiceless stops /p t k/ became the affricates /pf ts kx/, simplifying later to the geminate fricatives /ff ss (‘ƷƷ’) xx/ in certain environments. It has long been assumed that the affricates developed only from aspirated allophones of /p t k/, thus accounting for the retention of plain stops in /s/-clusters and a few other positions, but it is not obvious why particularly aspiration, ensuing from a laryngeal gesture of spread glottis, should have resulted in the oral property of affrication. Neither is it clear how etymologically simplex segments, upon deaffrication in certain environments, might have resulted in geminates without further stipulation. Proceeding from essentially traditional assumptions, and at the same time addressing important questions about Germanic phonetics raised by Vennemann (1984), the present paper attributes the triggering of the affrication event to an early factoring out, or segmentalization, of the feature for aspiration, i.e., pre-OHG [ph th kh] → [ph th kh]. Explanations are then proposed for the development of affricates out of these now disegmental sequences via place assimilation from the stops, and of the affricates into geminate fricatives (postvocalically and in some postconsonantal environments) via assimilatory weakening.