After the Kingdom of Romania entered World War I on the side of the Allies in August 1916, Macici fought in the Romanian Campaign.

[5] He rose to the rank of major general in October 1939 and was appointed commander of the 2nd Army Corps, stationed in Northern Dobruja, on 10 September 1940.

Macici fought with the 2nd Army Corps against the Soviets in the Danube Delta during Operation München, and later advanced towards Odessa.

The First Army suddenly had to fight the German troops based in Romania, but was able to hold the Carpathian Mountains passes until Soviet reinforcements arrived.

Macici remained at the head of the First Army and participated in the advance in Transylvania and joint Soviet–Romanian attack on Hungary and Slovakia.

[8] Nonetheless, in late 1944 the troops under his command took hold of the Budapest Airport and, at his order, flew the Romanian flag above it.

[1] He was put on trial in May 1945 for war crimes committed during the occupation of Transnistria, in particular, for the reprisals against the civilian population during the 1941 Odessa massacre.

The charges were brought before the Bucharest People's Tribunal and the presiding judge, Alexandru Voitinovici [ro],[9] by prosecutors Avram Bunaciu and Dumitru Săracu.

[2] In July 1995, the Romanian First Army Corps "General Nicolae Macici" was awarded its battle flag through a decree signed by President Ion Iliescu.