Some more info. The retreating troops are British expeditionary divisions lent to Spain (me). In both cases the same thing happened. The Brits began retreating to Spanish ships which are then attacked by commerce raiders (the American fleet is at the bottom of the ocean). The American attack disrupts embarkation—a good, sly tactic. In both instances, believing the troops have boarded ship, I moved the fleet. Later I see that the British troops are still there, marching back and forth with white flags.
They can not longer be selected so I assume its just their ghost sprites. Doomed to forever wander the American coast.