They were both able engineers but their systems were inferior to that of Cormontaigne.
In 1767 De la Chiche introduced a system of fortification in many respects original.

He raised his covered-ways so as to conceal all his masonry, and casemated a great portion of his _enceinte_.

For exterior defence, he employed direct fire from his barbettes, and curvated fire from his casemates; the direct fire of the latter secured his ditches.
Next to De la Chiche follows Montalembert, who published in 1776.

He was a man of much experience and considerable originality, but of no great ability as an engineer.

Most of his ideas were derived from De la Chiche and the German school of Rimpler.