Drawing his material from a range of primary sources in England, Germany and Australia, the author looks at the action at the Battle of Messines from all levels of command, including the soldiers' perspectives, during the preparatory, battle and post-battle stages. He reassesses the reasons for General Plumer's success on the day, the implications of Haig's failure to exploit that success, and the legacy of the battle for the maturing of the BEF in 1918. The attack is also examined from the viewpoint of the defending German troops on the other side of the wire. A study of the planning and execution of the Royal Engineers' tunneling and mining activities is also included.