The proper strategic point of passage is easily determined by
recollecting the principles laid down in Article XIX.; and it is here
only necessary to remind the reader that in crossing a river, as in
every other operation, there are permanent or geographical decisive
points, and others which are relative or eventual, depending on the
distribution of the hostile forces.

If the point selected combines strategic advantages with the tactical,
no other point can be better; but if the locality presents obstacles
exceedingly difficult to pass, another must be chosen, and in making the
new selection care should be taken to have the direction of the movement
as nearly as possible coincident with the true strategic direction.
Independently of the general combinations, which exercise a great
influence in fixing the point of passage, there is still another
consideration, connected with the locality itself. The best position is
that where the army after crossing can take its front of operations and
line of battle perpendicular to the river, at least for the first
marches, without being forced to separate into several corps moving upon
different lines. This advantage will also save it the danger of fighting
a battle with a river in rear, as happened to Napoleon at Essling.

Enough has been said with reference to the strategical considerations
influencing the selection of the point of crossing a river. We will now
proceed to speak of the passage itself. History is the best school in
which to study the measures likely to insure the success of such
operations. The ancients deemed the passage of the Granicus--which is a
small stream--a wonderful exploit. So far as this point is concerned,
the people of modern days can cite much greater.