In 334 B.C., Alexander the Great began the first of three major offensives against the Persian Empire with the Battle of the Granicus River. The significance of this battle was twofold; in Warfare in Hellas author Martijn Moerbeek points out that Alexander utilized this battle to secure the coast of the Aegean Sea and to open routes to other conquests. By closing access to the Aegean, Alexander rendered the Persian fleet useless and guarded against them attacking Macedon. The victory also liberated key Greek cities in Asia Minor from Persian control and garnered their allegiance, setting up easy access to take many coastal points in future battles.
In 333 B.C., the Battle of Issus would be the first of two epic battles between Alexander the Great and Persian King Darius III. In Alexander vs. Darius, the Battle of Issus 333 B.C., Jeff Jonas observes that an Alexander victory would result in free access to the Mediterranean Sea; therefore, decimating the entire Persian Fleet and giving him total control of Western Persia. Issus was fought on a very narrow battlefield which negated the much larger Persian army and resulted in Darius III suffering significant losses of troops. The resulting gains after Issus gave Alexander the necessary land, authority and confidence to press forward in his quest to take the Persian Empire.
The second and final battle between Alexander the Great and King Darius III was the Battle of Gaugamela in 331 B.C. The significance of
References: Gill, N.S. Ancient Classical History, 1999. http://ancienthistory.about.com/ Moerbeek, Martijn. Warfare in Hellas, 1997. http://monolith.dnsalias.org/~marsares/warfare/army/a_hoplit.html Jonas, Jeff. Alexander vs. Darius, The Battle of Issus 333 B.C. http://ancientbattles.com/Issus/Issus.htm