The drought caused a lack of resources in the region, which became an overwhelming factor for the Confederates.
(The drought; caused; a lack of resources in the region, which became an overwhelming factor for the Confederates) (a lack of resources in the region; became; an overwhelming factor for the Confederates)
The drought a lack of resources in the region
caused became
a lack of resources in the region, which became an overwhelming factor for the Confederates
an overwhelming factor for the Confederates