Which relationship requires a force to support another supporting unit?

The correct relationship described is one of reinforcing, which involves one unit providing support to another designated unit that is primarily tasked with conducting the operation. In this context, the reinforcing unit takes on a critical role that necessitates the provision of additional resources or firepower to ensure that the supported unit can accomplish its mission effectively.

Reinforcing relationships typically exist in scenarios where the main unit requires bolstering to meet an operational need, whether that is in terms of firepower, manpower, or other resources. This relationship is essential in military operations, as it enables the supported unit to achieve objectives that might otherwise exceed its capabilities.

The other options represent different support arrangements that do not necessarily imply that one unit is specifically tasked to provide direct support to another. General support, for example, indicates a broader support role without specifying which unit receives that support as a priority, and indirect support often refers to a more detached form of assistance that may not include the same level of immediate resource allocation. Thus, the reinforcing relationship is clearly defined by the direct and focused nature of the support it provides to another unit.