Jingo - Terry Pratchett

"Pratchett's writing is a constant delight. No one mixes the fantastical and the mundane to better comic effect or offers sharper insights into the absurdities of human endeavor." —Daily Mail
Commander Sam Vines, the Ankh-Morpork City Watch, and their compatriots must fight for their country (or something like that) when Discworld goes to war in this wickedly funny Discworld novel from New York Times bestselling author Terry Pratchett.
No one would dream of starting a war without a perfectly good reason . . . such as a "strategic" piece of old rock in the middle of nowhere known as Leshp. It isn't much of an island that rises up one moonless night from the depths of the Circle Sea—just a few square miles of silt and some old ruins. Unfortunately, this historically disputed lump of earth is once again floating directly between two proud lands, Ankh-Morpork and the city of Al-Khali on the coast of Klatch. And that's enough to ignite the inglorious international pastime known as "war."
It is, after all, every citizen's right to bear arms to defend their own. Even if it isn't technically their own. And even if they don't have much in the way of actual weaponry. Pressed into patriotic service, Commander Sam Vimes thinks he should be leading his loyal watchmen, female watchdwarf, and lady werewolf into battle against local malefactors rather than against Klatchians. But war is, after all, simply the greatest of all crimes—and it's Sir Samuel's sworn duty to seek out criminal masterminds wherever they may be hiding . . . and lock them away.
As two armies march, Vimes faces unpleasant foes who are out to get him . . . and that's just the people on his side. The enemy might be even worse.
The Discworld novels can be read in any order but Jingo is the 4th book in the City Watch collection and the 21st Discworld book.
The City Watch series in order:

Guards! Guards!

Men at Arms

Feet of Clay

Jingo

The Fifth Elephant

Night Watch

Thud!

Snuff