Complex sentence: Hardie died a year after the outbreak of the war, on 2 September 1915, at the age of 59, his death causing a vacancy in one of the two Merthyr Boroughs parliamentary seats.
Split into simpler sentences: Hardie died a year after the outbreak of the war, on 2 September 1915, at the age of 59. His death caused a vacancy in one of the two Merthyr Boroughs parliamentary seats.