How did defensive artillery fire work

Artillery is not an art, but a science
In the early days of artillery, therefore, this branch of arms was the ticket for ordinary middle-class people to become officers:
Such ranks were then traditionally reserved for the nobility, but they often could not read/write, let alone calculate, because they did not have to - but the latter is a skill that is quite advantageous in terms of ballistics
Sons of tradesmen and craftsmen had to be able to do arithmetic/calculations for obvious reasons.
Because early (black powder) artillery was also considered dirty and not very honourable, the highborn had little inclination to get involved in it, Which meant that for the "common man" with a certain basic education had an evolutionary niche opened up as far as leadership positions were concerned.

To cut a long story short; it is fair to assume that promising tactics and methods were developed and used by the "bombardiers" in pretty much every army.
Because mathematics is an international universal language

 

As an Electrical Engineer it should be simple.
I can understand Volts Current and Resistance, Phase Angle and Frequency, Capacitance and Induction
but gunnery is still all Chinese to me.
I was lucky as a lad to be with an Artillery Field Regt at HQ. Battery. The guns were P, Q and R Batteries.
We simply kept them in touch with each other and the outside world by telephone or radio.
Between RHQ, Battery CP's and OP
In the 1960's telephone was still regarded as safe and reliable. Line laying wasn't fun.
The Surveyors were a weird lot, most of them terrified of bangs. They went for a brew up when the guns opened up.
I assume that most were from the Army Reserve doing their annual duty.
Probably cooks and clerical, when on National Service.
Most people think that all Gunners fire the guns but they are in the minority in an Artillery Regiment.
It is the GPO and his gun crews who do that.

Bill Beadle Letter to his brother an officer in an HAA Regt. in the UK July 1944
I’d rather be a G.P.O. than any other rank in the artillery. Now my G.P.O. days are over I’m surer than ever.
As C.P.O. I have a motley gang of “specialists” “employed men” clerks and assorted riff-raff to administer,
cajole and pacify. No guns, very little esprit de corps and thousands of fiddling details.
In action one gets a certain satisfaction in running the Battery (the B.C. being most of the time with our infantry).
But out of action it is a dog’s game.
I have equally good reasons for not wanting to be a Captain or Major.
Colonel of course is a very pleasant and easy job indeed but the Captain and Major rungs on the ladder make the game not worth the candle!

 

The British Royal Garrison Artillery used a similar technique for triangulating adjustment from more than one station. There is a chapter on the technique in Garrison Artillery Training Vol. II (Siege) 1911. This saved ammunition compared to bracketing with a single observer, but required more observers and good communications between them. It was a good "siege" technique.