Was there any warning before the atomic bomb attacks of World War 2?

Yes, there was a warning to Japan that we (the USA) were going to drop an atomic bomb. They did not believe us. So we dropped the atomic bomb. We warned them again. By this time, they did not answer because they were scared that we were going to drop an atomic bomb. So we dropped another bomb. After that, they surrendered the war. So we won World War 2.

The first warning said (and i quote) "we are in possession of the most destructive explosive ever devised by man. A single one of our newly developed atomic bombs is actually the equivalent in explosive power to what 2000 of our giant B-29s can carry on a single mission. This awful fact is one for you to ponder and we solemnly assure you it's grimly accurate. Before using this bomb to destroy every resource of the military by which they are prolonging this unless war, we ask that you now petition the emperor to end the war…"

then the second: Then we sent another warning "Because your military leaders have rejected the thirteen part surrender declaration, two momentous events have occurred in the last few days. Radio Tokyo has told you that with the first use of this weapon of total destruction, Hiroshima was virtually destroyed. Before we use this bomb again and again to destroy every resource of the military by which they are prolonging this useless war, petition the emperor now to end the war. Act at once or we shall resolutely employ this bomb and all our other superior weapons to promptly and forcefully end the war."