Complex sentence: The Battle of Wagram (July 5--6,1809) was the most important military engagement of the War of the Fifth Coalition and took place on the Marchfeld plain, on the north bank of the Danube.
Split into simpler sentences: The Battle of Wagram (July 5--6,1809) was the decisive military engagement of the War of the Fifth Coalition. It took place on the Marchfeld plain, on the north bank of the Danube.