Why Gondor didn't use divide and destroy in 1944

[Hisoka Morrow]

Yes, as Gondor was set as interior stretagy position, it didn't use divide and destroy to handle the 1944 war, such as concentrating all their combat power to annihilate one of the frontal foes but divide it's forces instead or it's my misunderstanding, and it truly did so by having it's major army led by it's king intended originally, while expecting the southern front was the 2nd prior to target? Any JRRT sources can answer this?