Solar flares explosively release magnetic energy in the corona. They drive high-speed flows and are efficient accelerators of energetic electrons, protons and other ion species. Open scientific questions remain on many aspects of impulsive flare energy release, including the mechanisms controlling onset and the release of magnetic energy and electron and ion heating, acceleration and transport. The time is right for making progress on these questions. Multi-wavelength observations (radio, microwave, EUV/UV, soft and hard X-rays, and gamma-rays) are producing a wealth of new data. Particle measurements in the solar wind are poised to determine the full range of energetic particles produced in flares. Advances in numerical modeling are for the first time revealing powerlaw spectra of electrons and ions. The goal of the session is to bring together observers, modelers and theorists to discuss progress, new ideas and strategies for understanding impulsive flare energy release and its onset.