Imager's Battalion by L.E. Modesitt

So, the thing this book reminds me of greatly is grinding out levels in MMOs. Quaeryt is now a subcommander in King  Bhayar's army, on the move towards the heart of Bovaria, where they will attempt to defeat the Kharst's forces. He continues to try to improve the skills of his small band of imagers along the way, and they fight in small skirmishes against ambushing forces, for the most part, until near the end of the campaign, when Quaryt and his band may be required to sacrifice everything for the sake of Telaryn.

Quaeryt's marriage to Bhayar's sister, Vaelora, continues happily along, despite their separation. She must remain behind in the capital city, Solis, with Bhayar's wife, Aelina, to keep the High Holders and Bhayar's ministers from building their own empires while the king is in the field with his armies. He and Vaelora keep in touch by letter, discussing obliquely all matters political, and not so obliquely their love for one another. The political gamesmanship goes on in the field as well, when the field marshall in charge of the army and his cronies try to put Quaeryt's battalion in harm's way as much as possible, hoping to rid themselves of one who has so much influence with Bhayar.

Not the most inspired novel in the series, but a necessary novel to get Quaeryt where Modesitt wants him, I suppose.