Complex sentence: Following his graduation from high school he was drafted into the Austrian army, where he quickly rose to the American army equivalent rank of second lieutenant within an army regiment that was promptly dispatched to fight in series of heavy battles on the Italian front.
Split into simpler sentences: Following his graduation from high school he was drafted into the Austrian army, where he quickly rose to the American equivalent rank of second lieutenant. His army regiment was dispatched to fight in a series of heavy battles on the Italian front.