What does Daniel 8:6 mean?

In his prophetic vision (Daniel 8:1), Daniel sees a male goat moving at incredible speed (Daniel 8:5). This new arrival attacks the animal Daniel had first seen, a ram (Daniel 8:3–4). The goat charges at the ram with violent intent.

This picture dramatically previews what happened under Alexander the Great. His forces first attacked the Persians at the Granicus River in Asia Minor, which is modern Turkey, around May, 334 BC. A year and half later, approximately November 333 BC, Alexander battled Persian forces at Issus near the northeastern tip of the Mediterranean Sea. The great speed of Alexander's conquest was alluded to in Daniel's earlier vision (Daniel 7:6). An angel will explain this vision to Daniel (Daniel 8:7–8, 21–22).

Daniel's prophecy regarding the Greek and Persian conflict is so accurate that critics of the Bible claim the portrayal is written later and falsely attributed to Daniel. But there is no compelling reason to doubt the dating or author of this writing. The description of the conflict is accurate because God's Word is inspired and inerrant. It is true in every respect. Jesus fully endorsed the Scriptures in His High Priestly Prayer. Addressing the Father, Jesus said, "Your word is truth" (John 17:17).