Was there any efforts on either side of WW1 to make incendiary artillery shells to try and burn the enemies out of trenches.If there was were they ever used in battle?
The UK, The USA, and Japan all seem to have used White Phosporus mortar bombs during WW1. Primarily used for concealment (smoke screens), it is unclear whether any were used in an anti-personnel mode intentionally. Whether you classify a mortar as an artillery piece is another issue-- I do, but many do not. The US Army started experimenting with white Phosphorus artillery rounds (bigger than mortar rounds) in about 1920.