[1][2] The division's lineage begins with the Brigade "Valtellina" established in Turin on 1 August 1861 with the 65th and 66th infantry regiments.

[6] On 24 November, General Erwin Rommel ordered the Afrika Korps and Ariete to push east to relieve the Siege of Bardia and the frontier garrisons.

On 6 December the Axis forces received the order to retreat westwards and the Trieste formed the rearguard and fought delaying battles at Bir Bellafaa, Sidi Breghish, Alem Hamza, and Suluq.

The plan was for the German divisions to outflank the British defenders by marching through the desert to the South of Bir Hakeim, with the two divisions of the Italian XX Army Corps covering the Germans left flank: the Ariete would attack Bir Hakeim, and the Trieste would open a gap in the minefield north of the Bir Hakeim to create a supply route for the German divisions on their drive to the coast.

On 29 May the Trieste had broken through British lines and reached Got el Ualeb, while to the division's South the Battle of Bir Hakeim unfolded.

The Trieste then pursued the retreating British forces and clashed with rearguards at Sidi Omar, Mersa Matruh until reaching El Alamein in Egypt.

[9] The division lost two regimental commanders before being partly overcome by British attacks, but the delay of the Allied advance allowed German armored forces to launch a devastating counterattack.

On 23 October 1942 the British commenced the Second Battle of El Alamein and the Trieste initially formed the reserve in the North of the Axis line.

On 4 November the division's command and most of the 66th Infantry Regiment "Trieste" retreated to Fuka and thus escaped the destruction of Axis forces at El Alamein.

[1][2] The remnants of the German-Italian Panzer Army retreated to El Agheila, where on 26 November 1942 the Trieste's two infantry regiments were reorganized and brought back up to combat strength by accumulating the survivors of other divisions.

[2] Attached to the division during 1942:[2] Attached to the division during the Tunisian Campaign:[2] For its conduct during the Western Desert campaign the President of Italy awarded on 7 December 1951 to the 66th Infantry Regiment "Trieste" Italy's highest military honor, the Gold Medal of Military Valor.