Promise of blood is the first installment of the Powder mage trilogy by Brian McClellan. It’s a series I have mixed feelings about even though I really enjoyed it.
The powder mage trilogy is, alongside The shadow campaigns, one of the most visible examples of what is currently being called “flintlock fantasy”. Fantasy novels based in the goings on of 18th and 19th century Europe have been around for a long time, but specifically military novels focusing on the era are a more recent phenomenon. That the subgenre got a name when authors started writing books “full of machismo”* probably says something about the types of fans who obsess over genre labels and/or the biases of publishers.
*I’m paraphrasing a blurb here
Field Marshal Tamas has just initiated a coup. After overthrowing the government of Adro he must attempt to hold the nation together in the face of an invasion by their neighbor and historical rival, Kez. He also must contend with the possibly fictional curse that befalls the one who murders a sovereign, supposedly invoking the return of the gods.