Actually, the bomb did not end the war sooner, and the Russians entered the war before the second bomb was dropped. Internal Japanese records make it clear that the Russian invasion, not the nukes, was the key factor that led to Japan's surrender.
The Japanese moderates needed no convincing; they already wanted to accept the Potsdam Declaration, on the sole condition that the emperor not be deposed. The Japanese hardliners were the problem. The hardliners would not even agree to convene the Supreme War Council after they learned of Hiroshima, but they immediately agreed to convene the council when they learned that the Soviets had invaded Manchuria.
