This United States Army manual, Army Techniques Publication ATP 4-90 Brigade Support Battalion June 2020, describes the brigade support battalion (BSB) role, characteristics, core competencies, functions, organization, and operations in a brigade combat team (BCT) or multifunctional support brigade. This publication is a revision of ATP 4-90, Change 1, Brigade Support Battalion, last published in 2014. This Army techniques publication (ATP) was written for commanders, staffs, and Soldiers assigned to a BSB, BCT, or other functional and multifunctional support brigades. It provides relevant information on the capabilities of the BSB and BSB employment considerations. ATP 4-90 clarifies existing BSB doctrine. The ATP chapters are structured in line with the BSB's functions as opposed to its task organization. The updates to ATP 4-90 expands on the employment of a brigade support battalion. It provides detailed information on command and control including the operations process, sustainment support concept development, BSB in brigade support area operations, echeloning of BSB support capability in the BCT area of operation (AO), discussion on the two levels of maintenance, and other topics. Organization graphics are updated with organizational changes. This publication modifies the definitions of area support and echelon support. ATP 4-90 contains eight chapters and three appendices: an appendix on the BSB's mission essential task list with key collective tasks, security force assistance brigade (SFAB) appendix, and an appendix containing sustainment planning factors. ATP 4-90 chapters are: Chapter 1 includes the characteristics, core competencies, capabilities, functions, organization, and operations of the BSB to BCT and multifunctional support brigade. The chapter discusses how the BSB supports BCT execution of decisive action. Additionally, the chapter describes how the BSB supports the BCT's decisive action tasks during large-scale ground combat operations. Chapter 2 describes how the BSB commander and staff execute mission command by applying command and control. It describes how the command post is organized with functional and integrating cells. It describes the responsibilities of the commander and staff conducting the operations process and considerations for staff roles in the cells of the command post. Chapter 3 provides an overview of the BSB's support operations section. The chapter also includes information on creating and using a sustainment concept of support, staff running estimates, logistics synchronization matrix, sustainment overlay, and other key logistics planning tools. It also describes materiel management and its functions. Chapter 4 provides an overview of support areas at different levels and describes the fundamentals, operations, and considerations at the BCT level for the establishment, operation, protection, and displacement of the brigade support area. Chapter 5 provides an overview of how the BSB arrays forces and echelons sustainment across the battlefield to the brigade through the use of field, combat, and company trains. The chapter also discusses the use of a forward logistics element and echelon above brigade sustainment units that support the BCT. Chapter 6 provides an overview of distribution fundamentals at the BCT level and describes the role, organization, and operations of the BSB's distribution company, forward support companies, and other units that provide distribution support to the BCT. Chapter 7 provides an overview of maintenance fundamentals at the BCT level as well as describes the role, organization, and operations of the BSB's field maintenance company and forward support companies. Chapter 8 provides an overview of medical support at the BCT level as wells as describes the role, organization, employment, and operations of the brigade support medical company.