Militaries, governments, economies, and societies in the US and all over the world rely heavily on services provided via space systems. With a few exceptions, the world is designed around the assumption that space services will always be available. Even though it is understood that space systems may be quite vulnerable to disruption, no one is really ready for prolonged or severe down times. Space Force's sustainment mission is all about maximizing "up time" under all circumstances. This document, titled "Space Doctrine Publication 4-0, Sustainment," provides guidance and principles for the proper use of military spacepower in support of the United States Space Force's responsibilities. It covers topics such as the operational environment, fundamentals of sustainment, sustainment capabilities, and roles and responsibilities of organizations involved in space operations. The document emphasizes the importance of effective sustainment for enabling consistent and enduring space operations and fulfilling national security priorities. It also discusses the unique challenges and considerations involved in sustaining space capabilities and the need for collaboration and coordination among different entities. The document highlights the importance of considering sustainment early in the design and development process to optimize future system compatibility and interoperability. This annotated edition illustrates the capabilities of the AI Lab for Book-Lovers to add context and ease-of-use to manuscripts. It includes six types of abstracts, building from simplest to more complex: TLDR (one word), ELI5, TLDR (vanilla), Scientific Style, Action Items and Visual; four essays to increase viewpoint diversity: Context in the Discourse, Formal Dissent; Red Team Critique; and MAGA Perspective; and Notable Passages and Nutshell Summaries for each page.