Complex sentence: The Royal Navy's "E" class of diesel/electric submarines were built between 1912 and 1916 and were the mainstay of the submarine fleet during World War I. In total, 58 boats were built, including two constructed for the Royal Australian Navy.
Split into simpler sentences: The Royal Navy's E-class of diesel/electric submarines were built between 1912 and 1916 and were the mainstay of the submarine fleet during the First World War. A total of 58 boats were built, including two constructed for the Royal Australian Navy.