Sebastian le Prestre, Marquis de Vauban (1633-1707), was a French military engineer and adviser to King Louis XIV.
What Kilroy was to the twentieth century, Vauban was to the seventeenth. Wherever you went in Western Europe, Vauban had already been there and had designed, built, strengthened — or conquered — the fortifications.
Altogether, in his long career, Vauban repaired and strengthened the existing fortifications in three hundred places, conducted fifty-three sieges and built thirty-three completely new fortresses.
In 1673 Louis XIV joined Vauban near Maastricht with 45,000 troops for the purpose of overcoming the existing fortifications and occupying the city. Vauban accomplished this within three weeks, using new tactics of his own devising.
For the next five years Maastricht was occupied by the French, and in this time Vauban repaired and strengthened the fortifications. But in 1678 the French withdrew from Maastricht as agreed in the peace treaties of that ended the Franco–Dutch War. In return, France retained control of the region of the Franche-Comté and the city of Besançon, which in the meantime had also been successfully besieged by Vauban.
My photos in this post are from 2012. I revised the text in 2019.