From the late 19th century field artillery batteries started to become more complex organisations. First they needed the capability to carry adequate ammunition, typically each gun could only carry about 40 rounds in its limber so additional wagons were added to the battery, typically about two per gun. The introduction on indirect fire in the early 20th century necessitated two other groups, firstly observers who deployed some distance forward of the gun line, secondly a small staff on the gun position to undertake the calculations to convert the orders from the observers into data that could be set on the gun sights. This in turn led to the need for signalers, which further increased as the need to concentrate the fire of dispersed batteries emerged and the introduction fire control staff at artillery headquarters above the batteries.