Complex sentence: When the Germans attacked Poland in September 1939 O'Rourke was on a journey to Estonia and traveled via Warsaw and Königsberg to Berlin, where he applied for a Visa to Italy.
Split into simpler sentences: When the Germans attacked Poland in September 1939, O'Rourke was on a journey to Estonia. He traveled via Warsaw and Königsberg to Berlin, where he applied for a Visa to Italy.