Final answer:
British commanders such as Thomas Gage were appointed by the British Crown or government, and the command structure was hierarchical and disciplined. Roman Britain followed a military command structure led by legionary legates and centurions after the 43 CE by Emperor Claudius. The British also trained local leaders in their Empire for administrative and military roles.
Step-by-step explanation:
British commanders were appointed based on various criteria depending on the context and time period. During the American Revolutionary War, commanders like Thomas Gage, who was the commander of the British garrison in Boston, were put in charge by the British Crown or government. Notably, on April 14, Thomas Gage sent 1,000 troops to move against the colonials at Lexington and Concord. Earlier, Roman Britain was overseen by legionary legates, usually powerful nobles or politicians appointed by the emperor. During the initial invasion of Britain, leaders like Julius Caesar led the forces, but after the formal incorporation of Britain into the Roman Empire, in 43 CE by Emperor Claudius, it followed Roman military command structures including legates and centurions, like the First Spear who was crucial during battles.
At other times, such as the mobilization of forces in India and the use of local soldiers and administrators, British command could involve trained local leaders as part of the imperial strategy. Regardless of specific individuals, the structure of command within the British Army was rooted in hierarchy and discipline to maintain control over volunteer and conscripted soldiers drawn from various social classes and regions.