Firing short and long is known as “bracketing” the target. When you think about this, they not only had a trained crew, they had a trained observer. They may have even had a dedicated and trained person or persons for a Fire Direction Center (FDC). Most of the time, in order to save time, you don’t have the gunners doing the math with the firing tables. They are preparing the ammunition and making the necessary changes to the mortar’s deflection and elevation.
The observer would have to have communications to the FDC. He would be giving them directions to adjust the mortar. The article says that they didn’t have mortar rounds impacting to the right or left of the target. They were “long” and “short”. That probably means that due to the math involved and the quick time that effective fire was placed on the target and the fact that they weren’t adjusting left or right, the firing position of the mortar had been pre-planned.
It was a professional mortar crew firing from a pre-planned position with a professional observer who was placed to see the effects of the fire.
Blueunicorn6, you have it exactly correct! The three legs of effective mortar fire is, Gun Line, Fire Direction Control and Forward Observer.
I believe this was pre-planned and obviously incorporated all the tenants of a professional indirect fire team.
A great question would be: Did they have a Fire Support Coordination Cell which would imply that it was a battalion sized supported operation? You can bet that someone has the communications, at minimum, from the FO to FDC or Gun Line.