Which procedure involves issuing a warning order to subordinates?

The procedure that involves issuing a warning order to subordinates is to issue a WARNO. This step is crucial in military operations as it alerts subordinates about impending changes or upcoming tasks without the necessity of providing all details at that moment. A WARNO serves to inform the team of the commander's intent and provides initial instructions that allow subordinates to begin preparations for the upcoming operation. This can include logistical support, resource management, and coordination of activities among units, ensuring timely and efficient execution of plans once more information is available.

By issuing a WARNO, leaders help maintain momentum and readiness within their units. It facilitates a proactive approach to operations, allowing subordinates to prepare while details are still being finalized, ultimately leading to greater efficiency in executing the final plan. The other options do not specifically address the act of warning or preparing subordinates in advance of an operation.