Well, yes, it would have started with more bombs. Specifically, another hundred thousand tons, more or less, of the same relatively little bombs that the Allies had been dropping on mainland Japan since the Doolittle Raid in 1942. The atomic bombs were prototypes, and although more certainly could be produced, the United States did not have any others that could have been dropped soon after Nagasaki.

The real plan, however, was Operation Downfall, an amphibious invasion of Japan that may well have dwarfed Overlord (the Normandy invasion) in troops involved and casualties. It was divided into two parts. The first was Operation Olympic, the invasion of Kyushu (the southern island of Japan) which was being planned for November of 1945, and the second was Coronet in March of 1946, targeting the main island of Honshu. Coronet would have involved landing about a half million American and British soldiers near Tokyo with air and naval support from what would have been the largest fleet ever assembled.

Maybe the seizure of the imperial capital would have finally brought Japan to surrender, but after the carnage of Okinawa the Allies would not allow themselves to assume that anything but total destruction of Japan would end the war. There were still several million soldiers under arms, thirty million citizens, many of whom who would fight to defend their homeland, and about 10,000 kamikaze planes meant to devastate the Allied fleet as it attempted the landing on Kyushu. This is over five times the size of the kamikaze group at Okinawa.

Of course, the dropping of the atomic bombs, as well as the need to begin the invasion quickly were predicated by the actions of the third Ally, the Soviet Union. During the last month of the war, Soviet forces invaded Manchuria, and before long Stalin would have landed troops on mainland Japan as well, potentially leading to a split occupation as occurred in Europe. The timing of the Japanese surrender is not only important in terms of casualties and the rebuilding of Japan, but also in the politics of the Cold War. As we know, some of the bloodiest satellite conflicts of the US-USSR rivalry occurred in Southeast Asia, but the region's balance of power would have been much different with a partly Soviet Japan involved.

Casualty estimates for Operation Downfall are extremely varied, ranging from a few hundred thousand (which would still have nearly doubled US military casualties in WWII) to a few million. The most telling indication of the possible bloodshed, however, is the fact that a US soldier wounded in the Middle East today would receive one of the purple hearts which were produced in anticipation of this invasion which have also been sufficient for Korea, Vietnam, Desert Storm, Iraqi Freedom and every other combat action taken by the US armed forces since 1945.