He was promoted general of brigade
before the close of the campaign, and was subsequently employed in
fortifying the new Rhine frontier of France. His work as chief of
engineers in the army of Italy (1799) was conspicuously successful, and
after the battle of Novi he was made general of division. When Napoleon
took the field in 1800 to retrieve the disasters of 1799, he again
selected Chasseloup as his engineer general. During the peace of
1801-1805 he was chiefly employed in reconstructing the defences of
northern Italy, and in particular the afterwards famous Quadrilateral.
His _chef-d'oeuvre_ was the great fortress of Alessandria on the Tanaro.
In 1805 he remained in Italy with Massena, but at the end of 1806
Napoleon, then engaged in the Polish campaign, called him to the _Grande
Armee_, with which he served in the campaign of 1806-07, directing the
sieges of Colberg, Danzig and Stralsund. During the Napoleonic
domination in Germany, Chasseloup reconstructed many fortresses, in
particular Magdeburg. In the campaign of 1809 he again served in Italy.
In 1810 Napoleon made him a councillor of state. His last campaign was
that of 1812 in Russia. He retired from active service soon afterwards,
though in 1814 he was occasionally engaged in the inspection and
construction of fortifications. Louis XVIII. made him a peer of France
and a knight of St Louis. He refused to join Napoleon in the Hundred
Days, but after the second Restoration he voted in the chamber of peers
against the condemnation of Marshal Ney. In politics he belonged to the
constitutional party. The king created him a marquis. Chasseloup's later
years were employed chiefly in putting in order his manuscripts, a task
which he had to abandon owing to the failure of his sight. His only
published work was _Correspondence d'un general francais, &c. sur divers
sujets_ (Paris, 1801, republished Milan, 1805 and 1811, under the title
_Correspondance de deux generals, &c., essais sur quelques parties
d'artillerie et de fortification_). The most important of his papers are
in manuscript in the Depot of Fortifications, Paris.

As an engineer Chasseloup was an adherent, though of advanced views, of
the old bastioned system. He followed in many respects the engineer
Bousmard, whose work was published in 1797 and who fell, as a Prussian
officer, in the defence of Danzig in 1807 against Chasseloup's own
attack. His front was applied to Alessandria, as has been stated, and
c