The engineer staff of the French army at this period, consisted of four hundred and forty-nine officers, and there were four battalions of sappers, of one hundred and twenty officers and seven thousand and ninety-two men; six companies of miners, of twenty-four officers and five hundred and seventy-six men; and two regiments of pontoniers, of thirty-eight officers and nine hundred and sixty men.

On the contrary, the enemy's neglect of these things is one of the most striking of the many faults of the war, and his ill-directed efforts to destroy the great wooden bridge across the Danube, and the successful operations of the French sappers in securing it, formed one of the principal turning points in the campaign.
The same organization enabled the French to perform their wonderfully rapid and decisive movements in the Prussian campaign of 1806, and the northern operations of 1807.
In 1809, Napoleon's army crossed, with the most wonderful rapidity, the Inn, the Salza, the Traun, and other rivers emptying into the Danube, and reached Vienna before the wonder-stricken Austrians could prepare for its defence.

It was then necessary for the French to effect a passage of the Danube, which was much swollen by recent rains and the melting snow of the mountains.

Considering the depth and width of the river, the positions of the enemy, and his preparations to oppose a passage, with the disastrous consequences that would result to the French from any failure in its execution; taking all these things into consideration, Jomini pronounced it "one of the most hazardous and difficult of all the operations of War." Here the fate of the army depended, apparently, upon the skill and efficiency of the engineers and pontoniers, and nobly did they discharge the trust reposed in them.

When the pontons failed, tressel-bridges were substituted, and even fifty-four enormous boats were put in requisition.