The siege of Halicarnassus was fought between Alexander the Great and the Achaemenid Persian Empire in 334 BC. Alexander, who had no navy, was constantly being threatened by the Persian navy. It continuously attempted to provoke an engagement with Alexander, who would not oblige them. Eventually, the Persian fleet sailed to Halicarnassus, in order to establish a new defense. Ada of Caria, the former queen of Halicarnassus, had been driven from her throne by her younger brother Pixodarus of Caria. When Pixodarus died, Persian King Darius had appointed Orontobates satrap of Caria, which included Halicarnassus in its jurisdiction. On the arrival of Alexander in 334 BC, Ada, who was in possession of the fortress of Alinda, surrendered the fortress to him.

The wars of Alexander the Great were a series of conquests that were carried out by Alexander III of Macedon from 336 BC to 323 BC. They began with battles against the Achaemenid Persian Empire, then under the rule of Darius III of Persia. After Alexander's chain of victories against Achaemenid Persia, he began a campaign against local chieftains and warlords that stretched from Greece to as far as the region of Punjab in South Asia. At the time of his death, he ruled over most regions of Greece and the conquered Achaemenid Empire ; he did not, however, manage to conquer the Indian subcontinent in its entirety according to his initial plan. Despite his military accomplishments, Alexander did not provide any stable alternative to the rule of the Achaemenid Empire, and his untimely death threw the vast territories he conquered into a series of civil wars, commonly known as the Wars of the Diadochi.