Complex sentence: On the Portland Stone piers are engraved the names of over 72,000 men who were lost in the Somme battles between July 1916 and March 1918, most of whom died in the first Battle of the Somme between 1 July and 4 November 1916.
Split into simpler sentences: On the Portland Stone piers are engraved the names of over 72,000 men who were lost in the Somme battles between July 1916 and March 1918. Most of whom died in the first Battle of the Somme between 1 July and 4 November 1916.