When Lincoln issued the Emancipation Proclamation, he also authorized the army to recruit black soldiers. Nearly 200,000 men answered the call. Several thousand came from Canada. What compelled these men to leave the relative comfort and safety of home to fight in a foreign war? In African Canadians in Union Blue, Richard Reid sets out in search of an answer and discovers a group of men whose courage and contributions open a window on the changing nature of the Civil War and the ties that held black communities together even as the borders around them shifted and were torn asunder.