Fact:

The Tyrians’ decision to ally with the Persians and Egypt against the Macedonian ruler was the main cause that triggered the siege. Tyre had been a strategic coastal location in the war between the Persians and the Greeks. In his drive to conquer, Alexander needed to gain control over all areas along the Mediterranean coast. As the Phoenician cities had previously contributed to the Persian naval forces, Alexander knew that he would need to secure Tyre before advancing towards Egypt so that the Persians had no chance of attacking him once he had sailed from the coast. In other words, his ambition for visiting the island was not without regard to his military expansion.

According to one account, Alexander asked to be allowed into the temple of the God Melkart, one who used to be associated with the Greek God Herakles, but the Tyrians denied him entry asking him to make his sacrifice in the temple situated on the mainland instead. Their defiance enraged Alexander who ordered a siege of the fortress island.

The operations to advance towards Tyre began in 334 BC. Due to favorable natural and geographical conditions, Alexander was able to build a mole from the mainland to the city with the assistance of Macedonian engineers and Cypriot kings, including but not restricted to Pnytagoras of Salamis. After 7 months and despite the Tyrian men’s counter attacks, and the fire they set to the siege engines and watchtowers that Alexander’s army had put up, he still managed to capture the city after breaching one of its walls.