Complex sentence: An ammunition lorry was set on fire by burning grass and the sound was taken to be an Italian counter-attack from behind and when a platoon advanced towards the sound with fixed bayonets, some troops thought that they were retreating.
Split into simpler sentences: An ammunition lorry was set on fire by burning grass and the sound was taken to be an Italian counter-attack from behind. When a platoon advanced towards the sound with fixed bayonets, some troops thought that they were retreating.