Finally, this chapter summarizes the key findings from the case study, the statistical analysis of the ASHES project, and the infall study conducted as part of the GLASHES project. Together, these studies reveal the initial physical and kinematic conditions of dense cores in infrared dark clouds. This provides new insights into the earliest stages of high-mass star formation. The observational results are then compared with major theoretical frameworks, such as the core-fed and clump-fed models, to evaluate their consistency and constrain the physical processes that lead to high-mass star formation.