Was the atomic bomb the most effective way to force the Japanese to surrender?

Japan was putting out peace feelers by the summer of 1945. Their defensive position was in complete ruin: naval units gone, air force without fuel, most major army units immobile or cut off overseas. Their economy was in ruins - again lacking fuel, civilians in starvation rations, merchant marine gone, no trading ability, cities racked by conventional bombing. In hindsight we can see that Japan was clearly on the road to collapse and would most certainly have surrendered without an invasion of the home islands, if not in 1945, then in 1946. Nonetheless, hindsight was not available to the USA in 1945. At that time the US leadership had been appalled by the huge casualties to American forces (and Japanese) in the fighting for Iwo and Okinawa. Americans had witnessed mass suicide by Japanese civilians, Japanese soldiers carrying out suicide missions, Kamikazi raids, etc. To most Americans this meant that the Japanese were bent on self destruction rather than surrender. The Americans thus had two choices: (1) Invade the home islands of Japan, thus bringing about enormous (read: many millions) numbers of Japanese civilian dead. Such an invasion would likely have involved the Soviets leading to a partition of Japan similar to that of Germany, Austria, Korea. (2) Try and end the war quickly by shocking the Japanese leadership into quick surrender via the atom bomb. As horrific as the atomic attacks were, they most certainly prevented even more death and destruction from being hurled upon the Japanese by conventional forces.