Final answer:
Do not disregard elevation changes in military artillery calculations as they affect fire accuracy. Mills are 1/6400th of a circle and provide precise angular measurements critical for aiming at long distances.
Step-by-step explanation:
When considering artillery calculations or directional assignments in the military, you should not disregard a change in elevation when the difference could affect the accuracy of fire. The term 'mills' refers to a method used to measure angular subtense, which is important in ballistics and military applications. Mills are used in instances where precise adjustments are required, and a mill is equal to 1/6400th of a circle. This increment allows for granular adjustments and precise targeting. For example, adjusting a gun one mill would change the point of impact by one meter at a distance of 1000 meters. This degree of precision is critical when aiming at long distances or when even slight elevation changes can significantly alter a trajectory.