14 December 1940, the Siena repelled Greek probing attacks, but by 19 December the division retreated with the other Italian forces from the line between Himarë to Kallarat. The Siena was able to stop the Greek advance just short of the valley of Shushicë, on the mountaintops of Mali i Çorajt to Horë-Vranisht. The fighting was bloody, with the infantry regiments of the Siena down to battalion strength. On 24 December 1940 the 33rd Infantry Division "Acqui" arrived to stabilize the front and on 26 December 1940 the Siena was relieved from front line duties and sent to Berat to regroup. To plug the gap caused by the Greek breakthrough after the Capture of Klisura Pass the Siena returned to the front on 25 January 1941 along the line from Qafa e Kiçokut to Monastery Hill (Height 731) north of Këlcyrë. The division managed to stop the breakthrough, despite incessant Greek attacks. On 8 February 1941 the division once more was sent to the rear. After being rebuild the Siena participated in the Italian Spring Offensive, which started on 19 March 1941 and ended with disastrous results for the Italian troops. In April during the Battle of Greece the Siena captured Këlcyrë on 14 April 1941. On 16 April 1941 the Siena was ordered to stop, while the 47th Infantry Division "Bari" took over frontline duties. After the fighting ended the Siena was reorganized in the Osum valley. At the beginning of May 1941 the Siena was sent to the Peloponnese in Greece, where it formed garrisons in Corinth, Nemea, Argos and Nafplion. In late September 1941 the division was transferred to the eastern part of the island of Crete, where it assumed the title of Italian Troops in Crete Command (). On 1 March 1942 the division was reinforced by the LI Special Brigade. On 18 April 1943 parts of the Siena defeated an Allied landing attempt on the island of Koufonisia. The division, together with the LI Special Brigade remained in Crete until September 1943, when Italy signed the Armistice of Cassibile with the Allies. The German forces of the Fortress Crete disarmed the Siena and LI Special Brigade on 9 September 1943. In October 1943 about 2,000 Italian POWs from Crete were killed, when the ship MS Sinfra that transported them to mainland Greece was sunk by US and British planes. Another 2,670 Italian POWs from Crete