Typical battalion defensive frontages were 1000 yards, with one company up, one in support, one in reserve and one resting. So roughly one platoon per 250m, which funnily enough is also the average company assault frontage, and 200 men is roughly a company…
So, against your Germans you will have approx a platoon of Brits/French with whatever organisation is appropriate. For the Brits probably three rifle/bombing sections and a Lewis section. They would also be supported by medium MGs from the brigade/regiment MG companies, either entrenched directly in the front line or in support from positions a few hundreed yards back. Many of these guns would be sited to fire in enfilade along the front of the defensive system, ideally aligned with the wire obstacles. For a brigade with two battalions up you are looking at around 8 MGs in support per battalion (or two for our notional platoon if pro-rata).
They would also be supported by pre-registered trench mortar and artillery SOS barrages, generally these would create a beaten zone across the entire front and a minimum of 100 yards deep.
Bear in mind that the support trench is typically only 1-200 yards behind the front line trench, so reserves are readily available for counteratatcks.
The exact arrangment of the defensive positions varied, the French went for a strongpoint defense (strongly manned active sectors firing in enfilade over heavily wired passive sectors), whereas in 16/17 the British were more of a 'thin red line' approach.
How many of these defenders are still alive or unsuppressed when the assault goes in depends on how much artillery prep the attackers have done, and if the wire is uncut and the defenders alert, the trench garrison is easily capable of holding off all but the most determined assault, but this scenario sounds more like a large raid?
is back from Council of Five Nations.