Yepp what’s your question i might can help
They were able to unite because the Persian invasion of Greek mainland was a common threat for all, so they united to stop it. This was impossible before because Persia was not considered to be such a major threat.
The major reason for President Harry Truman’s decision to use atomic bombs against Japan was the "potential loss of American lives from an <span>invasion of Japan"</span>
End of the first century or the beginning of the second century
