Question

Why does FDR mention that the message received an hour before the attack contained "no threat or hint of an armed attack?"

Answer 1

The correct answer to this open question is the following.

Unfortunately, you did not specify the message Roosevelt received or the context of this event to know the time and the situation.

However, trying to help you we can comment on the following. We assume you are talking about the "Infamy Speech" delivered by US President Franklin D. Roosevelt after the Pearl Harbor attack of December 1941.

President FDR mentioned in that speech delivered at US Congress on December 8, 1941, that the message he received an hour before the attack contained "no threat or hint of an armed attack," letting the members of teh Congres and the American people know that the US had been the victim of a dishonest move on the part of the Japanese government and that the US never provoked or incited Japan to attack Pearl Harbor. That the US had been a victim of Japanese aggression and that was the reason why Roosevelt was asking Congress for a declaration of war against Japan.

That is how the United States entered World War II.