One of the most important and, often, one of the most difficult aspects of the strategic planning process is the development of a mission statement, that is, a brief, clear statement of the reasons for an organization’s existence, the purpose(s) or function(s) it desires to fulfill, its primary customer base, and the primary methods through which it intends to fulfill this purpose. The mission statement provides the context for the formulation of specific lines of business in which the organization will engage and the strategies by which the organization will operate; it sets the arena in which the organization will compete; and it determines how resources will be allocated by the organization and what the general pattern of growth and direction will be for the future. The primary purpose for having such a mission statement is to bring clarity of focus to members of the organization, to give them an understanding of how what they do is tied into a greater purpose. Thus the focus of the mission should be internal to the organization, not external for other stakeholders.

Applied Strategic Planning: How to Develop a Plan That Really Works
–Leonard D. Goodstein / Timothy M. Nolan / J. Willian Pfeiffer