Rivers as lines of defence.
It has been conceded, we believe, by military men, that rivers, in general, form but indifferent lines of defence.
It is almost impossible to prevent an enemy from crossing at some point on a long river, because if one be guarded he may turn it, and succeed by a flank movement, where he could not effect the passage by assault.
As a temporary barrier and a good place to make a stand, rivers nevertheless answer a good purpose.
But the instances in history in which great commanders succeed in crossing rivers with little loss, although powerfully defended, are innumerable.
The selection of the Adige for his line by
Napoleon, in 1795, may appear to conflict with this theory.--That, however, was an exceptional case.
The
Adige emptied into the sea, and as the Austrians had no naval force, it could not be turned in that direction.
Marshes impassable for troops with munitions of war extended from the
Gulf of Venice within a very few mile-of
Verona, where were
Napoleon's headquarters and the greater part of his troops.
Above the Adige flows through tremendous mountains, and these extend to within a few miles of
Verona, coming down to the very river, along which and on both sides run two narrow, difficult mountain roads, which it was easy to guard.
On the other side of the river — that is, on the same side with
Verona — was the
Venetian territory.
Napoleon had, therefore, only a very short space of the river — not more than a dozen miles — to guard.
On his left he was protected by the mountains, and on his right by the marshes.
It was difficult, therefore, to turn his position, yet it was turned by a portion of the Austrian army under
Warmer in August, who came around Lake Guards, while Warmer in person crossed it lower down with the bulk of his army.
The battles of Sonata and
Castiglione followed, with several combats, which in a week reduced Warmer to the necessity of flying from
Italy with the loss of half of his men.
Napoleon never conceived that the river could not be crossed, or his position turned.
But he saw that in effecting these operations, an enemy must so divide his forces as to expose them to destruction in detail.
Events amply justified his foresight.
There were four different attempts to relieve
Mantua, and it cost two large armies.
It strikes us that
Gen. Lee made the same calculation in arresting the advance of
Burnside at
Fredericksburg.
He knew that be could not prevent him from crossing, but he knew also, that his position was such that if the passage was made in front of him he could make him suffer severely.
If it were made elsewhere he would be compelled to abandon his line of communication, established with great labor, or divide his forces, and thus expose them to destruction.
Once on this side he would be compelled to fight him upon his own chosen ground, with a dozen other positions, all perfectly studied and understood, in his rear.
It is hardly probable that he could have prevented him, if he would; and it is not certain that he would have prevented him, if he could.
All he probably could do, or wished to do, was to make him pay for his passage, if he wished to fight
Burnside — which we presume he did — it was surely much better to make
Burnside come after him than for him to go across the river after
Burnside.
We observe that the
Yankees already begin to compare
Burnside's exploit with the two passages of the
Danube by
Napoleon in 1809--the first resulting in the battle of E ing, (the 21st and 22d May,) and the second in the
battle of Wagram, (6th July.) There is a considerable difference, however, we venture to suggest.
The first crossing, in May, was not opposed at all. Half the
French army had gotten over, when the bridges were destroyed — the
French say by a rise in the
Danube, the Austrians say by fireships launched by orders of the
Archduke Charles — and they were attacked, with their backs to the river, by an Austrian force three times as numerous as they were.
It was the bloodiest contest in which
Napoleon had ever been engaged.
It lasted two days, and resulted in the recrossing of the
French into the
Island of Loban in the night.
This battle was called the battle of E ing by the
French, and by the Austrians the battle of Aspera.
If
Napoleon was not beaten, he came very near to being so. He says he retreated because the bridges were destroyed, and he could not receive reinforcements.
The
Austrians say he retreated because he could not otherwise says his army.
Be that as it may, there was almost as little opposition to the second passage at there was to the first.
The
French were in the
Isle of Loban.
They had built several bridges where they had crossed before.
The
Austrians stood fronting these bridges and the river on the hills of the opposite shore, prepared to assault the
French and drive them into the river as soon as they should passover.
Napoleon, in the meantime, had secretly prepared floating bridges lower down, and in the night of the 4th of July, opening a tremendous fire on the Austrians at the point where the first bridges were constructed, he caused them to turn their whole attention there, while he launched his floating bridges below and landed a heavy force on their extreme left, causing them entirely to change their line of battle, which now faced down the stream, instead of fronting the stream itself.
In neither of these cases was there much real opposition, or many men killed, whereas
Burnside suffered severely in the passage.
Again, it was May and July when
Napoleon passed the
Danube whereas
Burnside has passed the
Danube in December.
