So who are these “enemies of the cross” Paul was referring to?
Paul was talking about the Jewish leaders who did not believe that Jesus was the Messiah. They were the Jews who refused to believe that the cross upon which Jesus their Messiah died was the means of their salvation rather than the law of Moses.
Today the “enemies of the cross” are those who insist it takes the cross of Jesus PLUS something else. This doctrine of limited salvation will meet its "destruction" when the cross is shown to have “accomplished” the salvation of all humans.
"...for we ourselves have heard Him, and we are aware that this truly is the Savior of the world." (John 4:42)
"And I, if I should be lifted out of the earth, shall be drawing all to Myself." (John 12:32)
"Jesus is saying to him, I am the Way and the Truth and the Life. No one is coming to the Father except through Me." (John 14:6)
"Then Pilate turned Jesus over to them to be crucified. So they took Jesus away. Carrying the cross by Himself, He went to the place called Place of the Skull (in Hebrew, Golgotha). There they nailed Him to the cross...After this, Jesus, being aware that all is already accomplished, that the scripture may be perfected, is saying...It is accomplished. And reclining His head, He gives up the spirit." (John 19:16-18, 28-30)
Humanity was saved by its Savior on that cross, and He will in the future change all enemies into friends.
"For our realm is inherent in the heavens, out of which we are awaiting a Savior also, the Lord, Jesus Christ, Who will transfigure the body of our humiliation, to conform it to the body of His glory, in accord with the operation which enables Him even to subject all to Himself.” (Philippians 3:20-21)
Friends of the cross have faith in what it accomplished - the salvation of all.