Dear Student,
a. The First World War, started in 1914 and ended in 1918-19
b. It was fought between the Triple Entente which included Britain, France, Russia , Italy and Triple alliance comprised of Austria Hungary, Germany
c. The alliance was formed on the principle of collective security ,where each member promised come to the rescue of others in case of an act of aggression /attack.
d. It started precisely on 28 July 1914 and lasted till 11 November 1918 that is 4 years, 3 months and 2 weeks.
Regards