Countenance of War — J.R. Tomlin

(THE BLACK DOUGLAS TRILOGY: BOOK II)

Scottish knight, James Douglas has at last won a small victory over the conquering English at the Battle of Loudoun Hill. His king, Robert the Bruce, commands James to continue his guerrilla war, using the only advantages they have: ambush and sneak attacks. Retreating deep into Ettrick Forest, James trains the men who flock to join his small, ragged army even as his attacks earn him the hatred and fear of the invaders. 

Greatly outnumbered, James uses every ruthless trick he knows until finally Scottish freedom is within sight. But his foe, Edward II, King of England, is determined to defeat them, and Scotland's survival will be decided through blood and steel.