Hello! While more can always be said, check out this answer to the same question by /u/restricteddata, as well as this section of the FAQ for more information on the dropping of the atomic bombs in general, as well as analysis on if it was considered a war crime.

The nearest thing to a surrender offer before Japan's conditional acceptance of the Potsdam ultimatum on August 10 (the day after the second bomb and the Soviet invasion of Manchuria) was a mid-July approach in Moscow (then still neutral in the Pacific war) as reported in US communications intercepts.

A US decrypt of July 12 related that foreign minister Togo had the previous day instructed ambassador Sato to “sound [Molotov] out on the extent to which it is possible to make use of Russia in ending the war”, and (in a follow-up message) to impress on Soviet leaders that “Japan has absolutely no idea of annexing or holding the territories which she occupied during the war”.

A second intercept of July 13 reported the proposed despatch of former premier Prince Konoe to Moscow as special envoy, urging Togo to tell Molotov that “His Majesty is deeply reluctant to have any further blood lost among the people on both sides, and it is his desire for the welfare of humanity to restore peace with all possible speed,” though ”so long as England and the United States insist unrelentingly upon unconditional surrender the Japanese Empire has no alternative but to fight on”.

A third transcript of July 17 reported Togo as stating that:

If, today, when we are still maintaining our strength, the Anglo-Americans were to have regard for Japan’s honour and existence, they could save humanity by bringing the war to an end. If, however, they insist unrelentingly upon unconditional surrender, the Japanese are unanimous in their resolve to wage a thorough-going war….we are not asking the Russians’ mediation in anything like unconditional surrender.

In the event, these efforts came to nothing, the Soviets replying on July 18 that they’d received nothing substantive to pass on to the western allies and didn’t know why the prince was coming. Sato explained a week later that the mission was to present a peace proposal with a view to Moscow passing it on, and to improve Soviet-Japanese relations, but there matters seem to have rested until Moscow’s August 8 declaration of war ended now waning hopes for mediation.

This seems to have been the sum of explicit peace efforts before the bombings, at least to the extent that US policymakers knew of them. No explicit Japanese proposals were forthcoming apart from the renunciation of wartime territorial acquisitions (which presumably didn’t yet extend to China), though Togo’s July 17 stipulation of “regard for Japan’s honour and existence” hints at the importance of preservation of the Emperor’s rule which was the condition contained in Tokyo’s August 10 note and accepted in modified form in Washington’s response, clearing the way to surrender.