most urgent of
dangers. Sebetendorff was soon assaulted by a French column, and
retreated, after Beaulieu's example, on the line of the Adige.
Buonaparte, profiting by the perilous adventure of Valleggio, instituted
a small corps of picked men, called _Guides_, to watch continually over
his personal safety. Such was the germ from which sprung the famous
Imperial Guard of Napoleon.

The Austrian had, in effect, abandoned for the time the open country of
Italy. He now lay on the frontier, between the vast tract of rich
provinces which Napoleon had conquered, and the Tyrol. The citadel of
Milan, indeed, still held out; but the force there was not great, and,
cooped up on every side, could not be expected to resist much longer.
Mantua, which possessed prodigious natural advantages, and into which
the retreating general had flung a garrison of full 15,000 men, was, in
truth, the last and only Italian possession of the imperial crown,
which, as it seemed, there might still be a possibility of saving.
Beaulieu anxiously waited the approach of new troops from Germany, to
attempt the relief of this great city; and his antagonist, eager to
anticipate the efforts of the imperial government, sat down immediately
before it.

Mantua lies on an island, being cut off on all sides from the main land
by the branches of the Mincio, and approachable only by five narrow
causeways, of which three were defended by strong and regular fortresses
or entrenched camps, the other two by gates, drawbridges, and batteries.
Situated amidst stagnant waters and morasses, its air is pestilential,
especially to strangers. The garrison were prepared to maintain the
position with their usual bravery; and it remained to be seen whether
the French general possessed any new system of attack, capable of
abridging the usual operations of the siege, as effectually as he had
already done by those of the march and the battle. His commencement was
alarming: of the five causeways, by sudden and overwhelming assaults, he
obtained four; and the garrison were cut off from the main land, except
only at the fifth causeway, the strongest of them all, named, from a
palace near it, _La Favorita_. It seemed necessary, however, in order
that this blockade might be complete, that the Venetian territory, lying
immediately beyond Mantua, should be occupied by the French. The power
of this ancient government was no longer such as to inspire much
respect, and Buonaparte resolved