On June 22, 1941, Romania joined Operation Barbarossa on the side of the Axis, in order to reclaim the lost territories of Bessarabia and Northern Bukovina, which had been annexed by the Soviet Union in June 1940. Macici fought with the 2nd Army Corps against the Soviets in the Danube Delta during Operation München, and later advanced towards Odessa. When the city fell on 6 October 1941 after a 2 month siege, Macici and his 2nd Corps took over the city's garrison. On 22 October, a bomb went off at the headquarters of the Romanian 10th Infantry Division, killing 67 people, including 16 officers. Marshal Ion Antonescu ordered reprisals against Jews and Communists; this event became known as the 1941 Odessa massacre. On 23 October, General ordered Macici to travel to Odessa, with the mission of installing General at the command of the 10th Infantry Division, to investigate the causes of the attack, and to organize military activity in the city. On 24 October, Macici received a telegram from Antonescu, ordering the execution of all Jews who had taken refuge in Odessa, as well as all people arrested in connection with the bombing; the order was carried out later that day by Lt. Colonels Nicolae Deleanu and Mihail Niculescu.