If an observer wants HE and then WP, what term would they use in the call for fire?

The term used in the call for fire to indicate a change in types of munitions, such as requesting High-Explosive (HE) rounds followed by White Phosphorus (WP), is indeed "followed by." This term clarifies the sequence and ensures that the supporting artillery or fire support unit understands that the observer wants a specific order in the firing sequence.

When an observer designates a request for HE, that constitutes the first request. By incorporating "followed by" into the call for fire, the observer effectively communicates that the second request, WP, comes after the initial HE rounds have impacted. This precise terminology is crucial for ensuring effective fire support as it helps maintain tactical coherence on the battlefield, aligning the fire support with the intended effects on target.

The other terms, while related to the context of fire support, do not serve the same purpose in this scenario. "Ammunition" refers to the types of munitions but does not specify the sequence. "Volume of fire" addresses the number of rounds to be fired over a given time, which is not relevant to differentiating types of munitions. "Projectile" describes the actual physical body fired, which also does not convey the intended order