This manual covers the basic knowledge and understanding on the conduct of the Philippine Army in the spectrum of military operations. It is the Army’s mother document for describing the broad roles and missions of the Philippine Army, which the essentials are underpinning for national security. It is divided into four chapters. The first chapter deals with the Philippine Army and the profession of arms, which explains the foundation and quality of the Army. The second chapter deals with the Philippine Army in the defense of the nation, as provided for in the 1987 Constitution and as reflected in the national military strategy. The third chapter deals with Philippine Army’s roles in the spectrum of the military operations. And, the last Chapter talks about the Philippine Army and the future security challenges.