World War I: First day on the Somme: On the first day of the Battle of the Somme 19,000 soldiers of the British Army are killed and 40,000 wounded.

World War I, or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Major areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. The war saw important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 15 to 22 million military and civilian casualties and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.