During the Romanian Campaign of 1916, he stood out at the battles of Perșani and Porumbacu, for which he was awarded the Order of the Crown of Romania, Knight class.
After an engagement with the Red Army at Brătușeni, his troops advanced towards the Dniester River, first in the direction of Mohyliv-Podilskyi, then towards Soroca and Bălți, and then playing a decisive role in the occupation of Chișinău on July 16.
That night, the division crossed the Dniester, and then served as the lead unit of the Romanian 4th Army (under the command of General Nicolae Ciupercă) in its advance towards Odessa, reaching the outskirts of the city by August 14.
After a disastrous attack on 18 August on the Karpova railway station (where the Soviets had dug in along the railbed embankments), Sion was relieved of his command by Marshal Ion Antonescu and replaced by General Carol Schmidt [ro].
Sion was killed on November 24, 1942 at Bolshaya Doshchinka, during the Battle of Stalingrad, when his 15th Infantry Division was overrun and wiped out during the Soviet Operation Uranus.