This paper gives a unified account of Grimm’s and Verner’s Laws in light of findings from experimental phonetics. The Germanic stress shift and stress placement shift are separate phenomena, and I argue that Iverson & Salmons’ (2003) shift in ‘articulatory setting’ corresponds to the former, and that the shift in how prosodic emphasis was expressed, from high pitch to dynamic stress, set Grimm’s Law in motion, because a phonetic correlate of dynamic stress is higher subglottal pressure. Increased subglottal pressure induced aspiration, affrication and spirantisation in Proto-Indo-European (PIE) voiceless stops and devoicing in voiced stops. The voiced aspirates became fricatives, which were allophones of voiced stops; these fricative allophones later fell together with the main plosive allophones to produce Germanic voiced stops.