Flames of Attrition - Vanessa Maclaren-Wray - Bog

The commander writes strategy in ink, the captain in orders, the trooper in blood.- Teachings of the Jeskan Guard
The nation of Jeska stands at a crossroads. As the newly-appointed king, Corren must contend with civilian distrust, an imminent invasion, and his fractured family. His wife and son are missing-trapped behind enemy lines. He's brought evidence the rising insurrection is funded by the shamans, but instead of disbanding that guild, the Council of Elders believes the enemy's lies that Corren's corrupt.
In days, an army of invaders-including hundreds of child conscripts brainwashed by the shamans and their allies-will march into Jeska. To save his country, Corren will need all his strategic genius, the determination of his guardsmen ... and dangerous new technology wrested from a device that doesn't belong in this world.