How did specialized military logistics units grow after the mid-19th century?

After the mid-19th century, the rapid increase in the technical complexity of warfare forced military establishments to move away from relying on civilians for essential services and instead incorporate a growing number of specialized, noncombatant skills directly into their ranks.1

This period saw the creation of many uniformed logistic services, such as the British Army’s Transport Corps, Hospital Corps, and Ordnance Corps. During the American Civil War, the Union army established a railway construction corps, while Prussia later created a specialized railway section within its Great General Staff to manage military-civilian rail operations.1

By the 20th century, these specialized units became common in the field. By the end of World War II, what was termed "service support" accounted for approximately 45 percent of the U.S. Army's total strength. Despite this growth, the military often acted as administrators over civilian specialists, as the sheer scale of modern war required vast networks of civilian scientists, technicians, and managers to operate the depots, factories, and communication centers necessary to sustain combat forces.1