What is the smallest organized subgroup of a convoy called?

The smallest organized subgroup of a convoy is referred to as a march unit. This term is used in military contexts to describe a specific group that has been organized for the purpose of moving together as part of a larger convoy. March units are typically comprised of elements from different units that are tasked with maintaining an effective level of command and control during movement, allowing for coordination and security while on the move.

In a convoy, march units serve to enhance efficiency in tracking and managing the progress of the vehicle movements, ensuring that formations can respond quickly to any challenges or changes in the environment. Their size can vary, but they are designed to be manageable units that can function effectively within the larger context of the convoy.

The other options pertain to different aspects of military organization but do not reflect the specific role of the smallest subgroup within a convoy setup. For instance, a serial refers to a sequence or order of march units, tactical groups typically indicate a larger collection of forces with a specific operational focus, and a company traditionally represents a larger formation of soldiers than what would constitute a march unit. Thus, the designation of march unit accurately captures the essence of the smallest organized convoy subgroup.