As we understand the Scriptures, the two witnesses represent the saints who, in the last days, will bear testimony concerning the soon coming of the Kingdom of God to the earth. These saints are an army of witnesses who will testify in the fullness of the power of the "latter rain." Their testimony will include many works of destruction of catastrophic proportions.
The evil of the end-time will be so great that God will issue a stern warning to all nations so they may prepare themselves for His coming.
The two witnesses will testify of the coming Kingdom and will illustrate the nature of the Kingdom by insisting on righteous behavior.