This is not about objectives, for someone with terrible intent can be strategically adept, but about deciding on a course of action that will not only fail to achieve its stated intent but will have negative consequences that far exceed the positive...

Most of my work has been in the military sphere where bad strategy invariably involves underestimation of opponents and overestimation of one’s own capabilities. In many cases far too much emphasis is placed on catching the enemy by surprise with bold early moves and not enough on the later moves, especially if the surprise attacks fail to achieve their objectives. Not enough questions are asked about the quality of the intelligence, the sustainability of the logistics, the resilience of the forces, the attitudes of allies. And these problems are aggravated with commanders who are too self-confident and fail to listen to take advice or ask the right questions of their subordinates. ...

Some bad strategies are the result of incompetence, miscalculation, and inattention. Most fail to consider how other key actors will behave. But the worst are the result of bad theories, so detached from reality that efforts are directed towards achieving goals that are unattainable, employing methods that are bound to fail. To extricate a country or an organisation from a bad strategy it is essential to acknowledge its wrongness and retreat, but with a truly bad theory that requires abandoning an embedded world view.

Lawrence Freedman, Article, "The Art of Bad Strategy" on his blog, "Comment is Freed".