Incorporating the lessons learned in the fighting at Passchendaele in the summer and early autumn of 1917, the first part of this official tactical summary of machine gun operations for October 1917 emphasises the importance of machine gun support of infantry operations by barrages. The second part of the booklet takes in the lessons learned in the battle of Cambrai in November 1917, including dealing with harassing aircraft. Taken together, and printed in one volume by the Naval and Military Press, these two official publications give an excellent picture of how lessons learned on the battlefield are quickly absorbed into tactical doctrines. They should be of consuming interest to anyone concerned with the evolving effects of machine guns on the western front in the Great War.