From the depths of the Circle Sea an island rises, only to be simultaneously discovered by a fisher from Ankh-Morpork and from Klatch. Soon both regions dispute over the new land, and when the ambassador from Klatch is nearly killed in an assassination in Ankh-Morpork, war seems inevitable. Commander Vimes, who tries to find out who really was behind the attack, sees his city taken over by war-hungry lords. These lords seem to think that victory over the foreign Klatchians will be easy, despite the fact that the Klatchians have fought many wars in the last decades, while the newly raised armies of Ankh-Morpork know war only from old tales and history.
The most chilling part of the book is when the little notebook demon of Vimes confuses two time lines, and we hear what happens to another Vimes and his Watch (all are getting slowly killed), where he has chosen to remain in the city to defend it, instead of following the captured Angela with his Watch into the faraway Klatch. The novel is like always about many things, but a strong theme is racism against people from another country, and that it is universal to far too many people on both sides.
Also it is about people who seem to think that war is just a game or a tool to further their own ambitions, and what happens if these people are in power. And whether or not one alone can hope that those people are brought to justice. Like always, where Vimes is the idealist, the Patrician is the realist and pragmatist who shows Vimes that sometimes it’s enough that the people survive, and that justice can come later.