Lines of Operation
A line of operation is "the area of land or sea through which we operate from our base or starting point to reach our objectives."
Lines of operation may be exterior or interior. We are said to hold the interior lines when we hold such a position, in regard to a theatre of operations, that we can reach its chief objective points, or forces, more quickly than the enemy can move to their defence or assistance. Such a position is called an interior position. "Exterior Lines" and "Exterior Positions" are the converse of these.
Lines of Communication
This expression is used of three different things:—
(1) Lines of supply, running from the base of operations to the point which the operating force has reached.
(2) Lines of lateral communication by which several forces engaged in one theatre of operations can communicate with each other and move to each other's support.
(3) Lines of retreat, which are usually lines of supply reversed, i.e., leading back to the base.
For naval purposes these three ideas are best described by the term "lines of passage and communication," which were in use at the end of the 18th century, and they may be regarded as those waters over which passes the normal course of vessels proceeding from the base to the objective or the force to be supplied.