When a Commander orders a UPL to conduct a monthly random test of 10% of Soldiers, which testing code applies?

The correct choice is Inspection Random (IR). This code is specifically utilized for instances where a Commander directs a UPL to carry out random drug testing on Soldiers. The term "random" in this context signifies that the selection of Soldiers for testing is not predetermined or based on any sort of predictable criteria; rather, it is done on a spontaneous basis to ensure fairness and compliance with regulations.

In this scenario, the Commander is requesting a monthly random test that includes 10% of the Soldiers, which directly aligns with the purpose and implementation of the IR code. This approach helps to uphold accountability within the unit and supports the overall mission readiness and health of the personnel.

The other options do not accurately represent the nature of the request. For instance, an Inspection Other would be too vague, Planned Assessment typically involves a structured testing schedule rather than random selection, and Routine Check usually refers to ongoing or scheduled testing rather than unscheduled random testing. Therefore, Inspection Random (IR) is the most appropriate code for this situation.