The strategist John Boyd described tactical work as a feedback cycle: observe, orient, decide, act — then observe again. The loop's insight is that tempo is the tactical virtue. The value of a tactic lies in how quickly one can act and learn from acting, not in how long any single action lasts; whoever cycles through the loop faster is setting the terms the other side must react to.
Boyd's emphasis complements the older boundary drawn by Carl von Clausewitz, who separated the levels by purpose: tactics is the use of forces within a single engagement, while strategy is the use of those engagements to achieve the larger objective. The engagement is the tactic; what the engagements are for is the strategy. Boyd adds the clock: the engagement level runs at the speed of feedback, which is why tactics must stay easy to abandon — attachment to any single action slows the loop, and the loop is the point.
See also: Policy, Strategy, and Tactics.