Page "Pathfinder (RAF)" Paragraph 18

To address these problems the PFF adopted new techniques.

Their force was split into three groups for each raid.

The " illuminators " would drop white target illuminators at points along the attack vector, allowing aircraft to follow these markers over long distances and thus avoid getting lost en-route.

The " visual markers " would drop coloured target indicators on the target, but only if they were sure it had been identified.

Finally the " backers-up " or " fire starters " used the visual markers ' flares as the aim point for their own incendiary bombs to light fires in the proper location, which would burn longer than the flares.