Complex sentence: This time the Italian advance was initially successful as the Bainsizza Plateau southeast of Tolmino was captured, but the Italian army outran its artillery and supply lines, thus preventing the further advance that could have finally succeeded in breaking the Austro-Hungarian army.
Split into simpler sentences: This time the Italian advance was initially successful as the Bainsizza Plateau southeast of Tolmino was captured. But the Italian army outran its artillery and supply lines, thus preventing the further advance that may have finally succeeded in breaking the Austro-Hungarian army.