How do tactics, operations, and strategy differ in military planning?

In military planning, theoreticians distinguish between three primary levels of activity, which differ in scope and purpose:1

• Tactics: These are the techniques and actions used to employ forces during an engagement, such as seizing a specific hill, sinking a ship, or attacking a target from the air. Tactics are concerned with the immediate approach to combat, the disposition of troops, and the execution of movements for attack or defense. They represent the art and science of fighting battles.123
• Operations: Often referred to as campaign planning, this level involves the use of multiple engagements in sequence or parallel to achieve larger objectives.1
• Strategy: This is the broad, comprehensive process of harmonizing military operations with political purposes. It involves the science or art of employing all of a country's resources—military, economic, and political—to achieve the objects of war.14

While these concepts are separable in thought, they are intertwined in action; every tactical decision inherently involves a strategic choice. Strategy is generally considered more strategic when a decision has long-term, less reversible effects, impacts a larger portion of a system, or focuses on the selection of goals.5