Brigadier Allan Mallinson gave the talk at Heathfield School in London Road to about 70 pupils last Tuesday.
He spoke about why and how Britain went to war in 1914 and why it was not over by Christmas, as many had hoped.
He gave an insight into the historical, political and military background of the conflict as well. After the talk he also invited the pupils to ask him questions both about the war, as well as his own career.
The school has also launched its new website. It can be visited at www.heathfieldschool.net