What is the primary purpose of Army Doctrine Publication (ADP) 4-0?

The primary purpose of Army Doctrine Publication (ADP) 4-0 is to describe the Army's sustainment system. Sustainment encompasses the logistics, personnel, and health services support necessary for operational success. By detailing the principles, processes, and components of sustainment, ADP 4-0 ensures that Army leaders understand how to effectively support their units throughout various phases of operations. This includes planning and executing logistics, managing resources, and ensuring that soldiers are prepared for missions. Understanding sustainment is crucial because it directly impacts the Army's ability to maintain readiness and effectiveness in both peacetime and combat scenarios.

In contrast, the other options focus on areas that are not the main domain of ADP 4-0. Recruitment strategies are more aligned with personnel management documents, combat strategies and tactics are addressed in different doctrinal publications focusing on operations and tactics, and financial audits of Army operations fall under financial management and oversight protocols, which are not covered within the scope of sustainment doctrine.