Slavery goes back that far but the war does not. You could trace some of the roots to Nazi Germany clear back to the 18th century but it wouldn't be fair to the Germans to say WWII actually broke out in say 1722.Um, not really... the point is that slavery stems from war. The enslaved were rendered into that position by warfare, and they and their descendents were kept there by what amounted to a decades-long low intensity conflict.
If you've read anything about American slavery, this is not controversial, as witness Baptist, Johnson, Stephanie Camp, Genovese, McCurry, Gutman, and Thavolia Glymph.
Ira Berlin's Generations of Captivity is excellent; Stephanie Camp's Closer to Freedom is well worth reading, as well.
It is basically a frame that asks the reader to recognized what is really being spoken of when one talks of "slavery." The phrase "plantation agriculture" conjurs up one picture - "slave labor camp" something else entirely, but the realities for the "targets" of the conflict was pretty close to the same thing.