The art of building military bridges is a special branch of military
science, which is committed to pontoniers or sappers. It is not from
this point of view that I propose to consider the passage of a stream,
but as the attack of a military position and as a maneuver.

The passage itself is a tactical operation; but the determination of the
point of passage may have an important connection with all the
operations taking place within the entire theater of the war. The
passage of the Rhine by General Moreau in 1800 is an excellent
illustration of the truth of this remark. Napoleon, a more skillful
strategist than Moreau, desired him to cross at Schaffhausen in order to
take Kray's whole army in reverse, to reach Ulm before him, to cut him
off from Austria and hurl him back upon the Main. Moreau, who had
already a bridge at Basel, preferred passing, with greater convenience
to his army, in front of the enemy, to turning his extreme left. The
tactical advantages seemed to his mind much more sure than the
strategical: he preferred the certainty of a partial success to the risk
attending a victory which would have been a decisive one. In the same
campaign Napoleon's passage of the Po is another example of the high
strategic importance of the choice of the point of crossing. The army of
the reserve, after the engagement of the Chiusella, could either march
by the left bank of the Po to Turin, or cross the river at Crescentino
and march directly to Genoa. Napoleon preferred to cross the Ticino,
enter Milan, effect a junction with Moncey who was approaching with
twenty thousand men by the Saint-Gothard pass, then to cross the Po at
Piacenza, expecting to get before Mélas more certainly in that direction
than if he came down too soon upon his line of retreat. The passage of
the Danube at Donauwerth and Ingolstadt in 1805 was a very similar
operation. The direction chosen for the passage was the prime cause of
the destruction of Mack's army.