The Army was kept in reserve during the brief offensive against France; during this period Vercellino drafted Plan T1, for the invasion of Ticino, which however was never put into effect.

German foreign minister Joachim von Ribbentrop complained to Mussolini that "Italian military circles... lack a proper understanding of the Jewish question.

"[6][7][8][9][1][2][3] In the late summer of 1943, owing to the deteriorating situation in Italy, a decision was made to repatriate the Fourth Army, handing over the occupation zone in France to the Germans.

The withdrawal from France was underway when the Armistice of Cassibile was announced, on 8 September 1943, and German forces initiated Operation Achse; the Fourth Army, dispersed between France, Piedmont and Liguria, was attacked by the converging forces of Field Marshals Gerd von Rundstedt, from Provence, and Erwin Rommel, from Italy, gradually disintegrating between 9 and 11 September.

On the same day, Vercellino was captured by the Germans along with his staff and imprisoned initially in Toulon and later in Germany, where he was held as a prisoner till the end of the war.