He heard that Vieilleville, who had become governor of Metz, was setting about the reduction of Thionville, "the best picture of a fortress I ever saw," says Montluc.

"I have heard," wrote Guise to Vieilleville, "that you have a fine enterprise on hand; I pray you do not commence the execution of it, in any fashion whatever, until I be with you: having given a good account of Calais and Guines, as lieutenant-general of his Majesty in this realm, I should be very vexed if there should be done therein anything of honor and importance without my presence." He arrived before Thionville on the 4th of June, 1558.
Vieilleville and his officers were much put out at his interference.
"The duke might surely have dispensed with coming," said D'Estrees, chief officer of artillery; "it will be easy for him to swallow what is all chewed ready for him." But the bulk of the army did not share this feeling of jealousy.

When the pioneers, drawn up, caught sight of Guise, "Come on, sir," they cried, "come and let us die before Thionville; we have been expecting you this long while." The siege lasted three weeks longer.

Guise had with him two comrades of distinction, the Italian Peter Strozzi, and the Gascon Blaise do Montluc.

On the 20th of June Strozzi was mortally wounded by an arquebuse-shot, at the very side of Guise, who was talking to him with a hand upon his shoulder.