Experience has taught me that there are distinctions between the different planning concepts (and that they can be worked together).
A business plan is a document, generally projecting three to five years into the future about the route a company intends to take to maintain and grow revenues. It incorporates the basic elements of market research, promotional strategies, operational requirements, and financial projections. There are many variations and sub-categories of each element described above, but all are focused on addressing the undeniably important, overall components of operating a business enterprise. The plan will be used for raising capital, expansion, reorganization of resources and activities, downsizing, and/or preparation for sell-out.
A strategic management plan addresses one or more of the elements of a business plan, but the primary focus is on the management team and its personnel. It may incorporate the development of manuals of operation, procedure, policy, and/or organization. Ultimately, the objective is to maintain or improve productivity, maximize internal control of resources, and enhance relationships (internally and/or externally).
A strategic management plan fits primarily into the operational aspects of a business plan where you list staff requirements, management philosophy, key personnel descriptions, and the credentials of the key personnel.
A third document is the strategic business plan. This document is generally a five year projection, and very generalized as to detail. It focuses on developing and defining long-term goals and objectives of the company. It may also incorporate timelines for the accomplishment of milestones.
I have written and continue to write business plans. I developed strategic management documents in the past, but they were not directed to timelines or financial projections. They focused primarily on management philosophies, organizational development and charts, definitions of policies, operations and procedures with flow charts, and development of forms implemented in the procedures.
I have written only one strategic business plan in my life. And I have read some books on the demise of the generalized document. I believe it has its place in those companies that are on the verge of writing or rewriting a business plan, but lack significant focus by which to develop that document.
Remember there is much divergence in the definitions of the three documents I have described. I provided definitions based on my experience, not textbook interpretations.