Duncan Grant is an officer in the British Army.
When we first meet him, he holds the rank of Colonel and is happy serving in His Majesty's army. Then he gets seconded to Military Intelligence during the First World War and his life will never be the same. The knowledge he learns in the cloak and dagger world will combine what his already impressive knowledge of military tactics to make him a formidable planner and, in some cases, schemer.
When he retires from the military, his old boss in the Intelligence field will call upon him to handle a few special problems for which he is the best solution. His personal objectives, though, will be definitely his own for what he saw during the War will make him forever against war and he will pretty much devote his life to preventing it.
But sometimes to achieve peace at a high level, he will have to foster insurrection at a lower level and in the course of his recorded career, he will stop a revolution in one place while urging one on in another.
More when I have finished the books.