_Concentric lines_ are such as start from distant points, and are
directed towards the same object, either in the rear or in advance of
their base.

If a mass leaves a single point and separates into several distinct
corps, taking divergent directions, it is said to pursue _eccentric
lines_.

Lines are said to be _deep_, when the end to be attained is very distant
from the base.

The lines followed by a secondary or auxiliary force are denominated
_secondary lines_.

The lines pursued by the army of the Sombre-et-Meuse in 1796, and by
Bagration in 1812, were _secondary lines_, as the former were merely
secondary to the army of the Rhine, and the latter to that of Barclay.

_Accidental lines_ are those which result from a change in the primitive
plan of campaign, which give a new direction to the operations. These
are of rare occurrence, but they sometimes lead to important results.

The direction given to a line of operations depends not only on the
geographical situation of the country, but also on the positions
occupied by the enemy. The general plan of campaign is frequently
determined on previous to beginning operations, but the choice of lines
and positions must ordinarily result from the ulterior events of the
war, and be made by the general as these events occur.

As a general rule, _a line of operations should be directed upon the