This is the third book in the Royal Marines series.

For three generations, members of the Blackwood family served the Royal Marines with distinction. With the outbreak of World War I, at last comes Jonathan Blackwood’s turn to carry the family name into battle.

But as the young marines embark for the Dardanelles, and a new kind of warfare, it dawns on them that the days of scarlet coats and an unchanging tradition of honour and glory have gone forever. First in Gallipoli, and two years later in Flanders, comes their horrifying initiation into a wholesale slaughter for which no training could ever have prepared them.

Caught up in the savagery of a conflict beyond any officer’s control, Blackwood’s future rests on the "horizon"—the dark lip of the trench which was the last fateful sight for so many.