on the Mexican American War, the Civil War and the expantion of the Confederate States is a bit confusing, but makes more sence if you read over the bad history telling of Confederates in US positions and imagine a time on horse backs in an region with a very lot of large distances and sadly almost equal fire power between Slave Owners and Free Men.
No slave ever was asked into slavery and willingly got there. Slave owners use every trick and violance to create slaves working for them abusing psychology, laws and weapon knowlege being around expanding and fighting back their nations since several thousand years ago as Mayans, Egyptians, Romans, Confederates and Nazis.
The Nazi Konzentrations Lager were strongly fortiefied and heavly guarded facilities according to the technological available to the NAZI nation on highest possible standards.
Of course, the Confederate Slave Farms reached the same levels just according to their times. It was easier to hijack their ships than attack a Farm.
Today these mindsets have still a nation and also secret services.