[Jerminator00]

During this period, Japan had a culture heavily focused on Honor. Surrendering was literally not an option for them, as they would rather die fighting than live in defeat, and the American military experienced their savagery and determination first hand. After the first bomb was dropped the emperor refused to accept surrender. That's when we dropped the second and said we had plenty more to drop if japan continued to refuse surrender (we did not, in fact, have more than 2 bombs. That was merely a bluff that worked in our favor.) After the second bomb, the emperor of japan conceded defeat, and then had to tell his own country not to commit suicide over the defeat.

So yes, they were necessary as they most definitely lowered the death count, and prevented the Japanese from driving themselves to extinction.