Géza Jablonszky was born in Budapest to father János Jablonszka and mother Mária Krivinyja.
He fought on the Isonzo front from May 25th, 1915. He was promoted to Lieutenant on August 1st, 1915, and a year later to First Lieutenant. As an artilleryman of the Imperial and Royal 3rd Mountain Brigade of the Austro-Hungarian Army, he fought in the area between Krn and Mrzli vrh and, in 1916, led the construction of the Memorial Church of the Holy Spirit in Javorca.
He collaborated very well with Remigius Geyling, the concept author of the church. On March 29th, 1917, he was awarded the Golden Cross of Merit for his sacrifice in the construction.
On January 3rd, 1917, Géza married Ilona Rösler. He proved to be a good builder even after the war: in 1924, in the construction of a monument in memory of the fallen in the First World War in Solymár; and in 1927, in the restoration of the Roman Catholic Church in the same place.