High Energy Astrophysics (observations of X-ray and gamma rays coming from celestial bodies) plays a key role in understanding the universe. These radiations reveal the processes in the hot and violent Universe. High Energy Astrophysics probes hot gas in clusters of galaxies, which are the most massive objects in the Universe. It also probes hot gas accreting around supermassive black holes in the centers of galaxies. Finally, high-energy radiation provides important information about our own Galaxy. Neutron stars, supernova remnants and stars like our Sun emit copious amounts of high-energy radiation. Europe plays a leading role in high-energy astrophysics research. The XMM-Newton and the Integral missions are leading the exploration of the X-ray and gamma-ray Universe. ESA‘s mission ATHENA to be launched in 2028 will carry the most sensitive X-ray telescope ever to be the flagship of all high X-ray missions. AHEAD 2020 is a project funded by the European Commission in the framework of Horizon2020 (Access to large-scale facilities). It is led by IAPS/INAF in Rome and involves most Universities and Research institutes which are involved in High Energy Astrophysics in Europe. The project aims to combine the efforts of all these Institutes in the analysis of X-ray data and facilitate access to infrastructures distributed across Europe. High-Energy Astrophysics has entered a new era, with a number of operational and near-future instruments being deployed in space, and a large X-ray observatory, Athena, being built for a launch around the beginning of the next decade. These facilities play a fundamental role in the new venue of multimessenger astronomy, as shown by the groundbreaking discovery of the electromagnetic counterparts to the gravitational wave event GW170817 observed by LIGO/Virgo, or to the neutrino source TXS 0506+056. AHEAD2020 aims at bringing the high-energy astrophysical and multimessenger community to an advanced level of integration by strongly focusing on networking and standardization, and by establishing common access procedures to facilities. Such effort of integration relies on the progress achieved with AHEAD but also on the strong links already in place between the high energy, gravitational and neutrino communities, as demonstrated by the recent discoveries in the field.