Which of the following best describes the operational level of war?

The operational level of war focuses on the planning and execution of campaigns and major operations that bridge the gap between tactical engagements and strategic objectives. Option B accurately reflects this by emphasizing the collective forces in a theater. At this level, commanders orchestrate various operations to achieve specific objectives that align with overall strategic aims, considering the integration of different branches of service and the coordination of resources across a broader area of operations.

While the other options touch on aspects of military operations, they do not encapsulate the operational level's essence. The details of individual engagements pertain more to the tactical level, where specific battles or skirmishes are conducted. Long-term strategic planning relates closely to broader national goals and directives, which generally fall within the strategic level of war. Management of resources is an essential function at all levels, but it does not specifically denote the operational level's focus on how those resources are combined and utilized to achieve larger military objectives within an operational context.