In November 1938 he was appointed commander of the Corpo Truppe Volontarie, the Italian Corps that fought in the Spanish Civil War.

On 24 November 1941, during the Totensonntag Battle, Rommel sent a telegram to Rome asking German military attaché in Italy, General Enno von Rintelen, to persuade Mussolini to place Gambara under his command.

Mussolini answered Rommel's requests by anointing him as commander of the Axis troops in Marmarica and placing Italian XX Army Corps at his disposal.

By November 23, the Ariete with assistance from the Trieste and Savona Divisions, had knocked out about 200 British tanks, and disabled or destroyed a similar number of vehicles.

[7] On March 3, 1942, Gambara was replaced as Chief of Staff of the High Command in North Africa by lieutenant general Curio Barbasetti di Prun.

[8] From December 1942 Gambara commanded the XI Army Corps, which was involved in anti-partisan operations and brutal repression of the population in Slovenia.

Fifteen hundred innocent people died In the Rab concentration camp from hunger, privation, and lack of medical care.

When the High Commissioner for the Province of Ljubljana Emilio Grazioli turned to him to complain about the harsh treatment meted out to those who had been interned ('absolutely all of them reveal the most severe evidence of lack of activity and starvation'), Gambara harshly answered him: “A concentration camp does not mean a fattening camp; a sick individual is a quiet individual.”[10] After the Kingdom of Italy joined the Allies, he was appointed Chief of Staff of the National Republican Army thanks to Rodolfo Graziani’s nomination.