Unity of command is a management principle that states that each employee should receive orders and be accountable to only one superior. Among the techniques of Scientific Management, the one that violates the principle of Unity of Command is:

Functional Foremanship

Functional Foremanship, as proposed by Taylor, involves the appointment of eight specialists to assist and support workers. This system allows workers to receive orders and instructions from multiple specialists, thus deviating from the principle of Unity of Command, which emphasizes the importance of a single line of authority and a clear reporting structure within an organization.