8-inch howitzer battery under fire, near Boesinghe, 17 August 1917. In the build-up to the Third Ypres campaign the BEF had to fight a long and painful counter-battery battle. This photo shows a tiny fragment of that battle: a near-miss on a single battery, close enough that even the veteran troops are ducking for cover. The Germans eventually lost the struggle to destroy the British guns, but they switched their tactics to harassing fire to deny rest to the British gunners (including using various gasses) and damaging communications routes, like the plank road here.
Source: IWM photo Q5889.