Fate's Ransom (The First Argentines Book 4) by Jeff Wheeler

Ransom Barton has served three Argentine kings. The new successor to the throne is the ruthless Jon-Landon, a fallible strategist when it comes to war. After losing against the Occitanian armies, the king forces Ransom to bear the blame and removes him from the council. But Jon-Landon isn’t yet through with humbling the honorable knight of Ceredigion.

When a retaliatory battle succeeds, Jon-Landon invites Ransom back into his circle. Though Ransom’s Fountain magic is made stronger by his fealty, he’s once again forced to make a terrible choice. And this time, Ransom’s wife, Claire, and their sons could pay the price for Ransom’s loyalty.

But as tensions between Ceredigion and Occitania reignite and alliances at court begin to crumble, a desperate Jon-Landon discovers his only ally is the knight he betrayed. With the future of Kingfountain hanging in the balance, Ransom agrees to help. And as secret enemies reveal their endgame, Ransom knows that he may have to make the ultimate sacrifice for the survival of the Argentine dynasty.