Complex sentence: Charles enlisted in the army (19th Hussars Glocstershire regiment) and was commissioned as Second Lieutenant in the first World War seeing action in Ypres, the Somme and many other campaigns.
Split into simpler sentences: Charles enlisted in the 19th Hussars Glocstershire regiment and was commissioned as Second Lieutenant in the first World War. He saw action in Ypres, the Somme and other campaigns.