During World War II, morale studies were made of the troops (Ref:1). Analyst expected Negro troops in the South to have a lower morale than Negro troops in the North; yet upon investigation they found contrary results.
The Negro recruit related his current Army status and pay to that of the local Negro community, not to an absolute scale.
So army Negroes in the South had more available funds to spend than the local males therefore they were able to afford more luxuries and attract local Negro women.
However, the lot of the Army Negro in the North was worse, by comparison to the industrially employed Negro male. In the North, the industrially employed Negro, enjoyed the advantage of relative luxury and female admiration, which they could not enjoy being in the army.
The relative deprivation of the Northern Army Negro lowered his morale.
Ref 1: S. A. Stuffer, et al., “Measurement & Prediction” (Vol. IV in Studies in Social Psychology in World War II), Princeton University Press, Princeton, N.J., 1950