I once sat in a meeting of project and business updates and suddenly one of the directors said, actually with all that we have now we can be in the medical device market. Violaaa!!! This medical device company used to service government hospitals and they have all the equipments. It's just that they never thought of going direct to the hospitals and take the lion share of the business. In that meeting, after going through the company yearly updates, this "innovation" came instantaneously and the next year they are pitching about it to the government hospitals directly.
Therefore, a marketing plan, according to Kotler, is a "written document, which includes the objectives, strategies and action plans regarding the elements of the marketing mix which facilitate and enable compliance with the strategy dictated at the corporate level".