Economic hardships forced his family to move to the Kingdom of Romania, to the newly acquired province of Northern Dobruja.

He crossed the border and went to Predeal, ostensibly for health reasons, and then on to the Timiș Valley and Brașov to buy an overcoat, but in reality he was scoping out possible attack routes for a Romanian incursion into Austria-Hungary.

[2] After Romania entered World War I in August 1916, Șteflea was given the command of a machine gun company in the 34th Infantry Regiment [ro], holding the rank of captain.

After the defeat of the Legionnaires' Rebellion in January 1941, he was appointed commander of the 3rd Infantry Division, with which he participated alongside German troops in the Siege of Odessa in the fall of 1941.

On 20 January 1942 he was appointed Chief of the Romanian General Staff, a position he occupied until the fall of the Ion Antonescu regime on 23 August 1944, as a result of King Michael's Coup.