By the third week of May the situation in the Mormal Forest had turned to disaster. Rommel's raid through the French lines toward the Sambre River scattered French units, and panzers rushed about in an orgy of breakthroughs and encirclements.

Ordered to clear the forest of Germans, Gen. Gustave Mesny of 5th North African Infantry Division knew that to be impossible and tried for an orderly withdrawal instead. Mesny gathered what forces he could and made his move in the middle of the night.

Mesny moved out with the lead French units at midnight and soon ran into enemy columns in the dark. Unexpected encounters with enemy minefields and anti-tank obstacles slowed his progress further, and the now-alerted 4th Panzer Division began to send infantry, engineers, tanks, artillery and even FlaK units to intercept the French. At 0600 the avant-garde had reached the Escaut River with only minimal losses, but the rear guard faced intense fighting. A company of Moroccans went back to help their comrades but 88mm and tank fire between Louvignies and Englefontaine blocked them. At 0745 the Tunisians and Moroccans assaulted the German defenses while singing a prayer for the dead. Their attack collapsed under the fire of tanks, machine guns and AA guns, with most of them killed or captured. Only small, scattered groups eventually reached the Escaut during the night of May 21st.

Mesny himself escaped the Mormal Forest to lead the remnants of his division fighting in the Lille Pocket; he was captured at the end of the month and spent the next four and a half years in German prisons. In December 1944 French guards killed an imprisoned German general, Fritz von Brodowski, who they held responsible for the massacre of 643 French civilians at Ouradour-sue-Glane and 117 more at Tulle, among other atrocities. In retaliation, Adolf Hitler personally selected Gustave Mesny for murder; Mesny was told that he would be transferred to another prison, and instead his guards shot him by the side of a highway. Mesny had helped Henri Girard escape in 1942, and this seems to have marked him for death.

Mesny had declined an opportunity to escape only days before his murder, as he feared that the Germans would murder his son, Louis, ifhe did so. Louis, also a prisoner of the Germans, was murdered by his captors anyway in April 1945.