At the beginning of the First World War, Allenby commanded the 1st Cavalry Division from August to October 1914, when his division played a crucial role in the retreat after the Battle of Mons By the First Battle of Ypres, in October and November 1914, he had been promoted General in command of the Cavalry Corps.
I begyndelsen af 1. verdenskrig havde Allenby kommandoen over 1. kavaleridivision fra august til oktober 1914, hvor hans division spillede en afgørende rolle i tilbagetrækningen efter slaget ved Mons Ved det Første slag ved Ypres, i oktober og november 1914, var han blevet forfremmet til kommanderende general for kavalerikorpset.