Final answer:
The fighting unit in the Macedonian army that was responsible for helping Alexander the Great defeat the Persians was the Phalanx.
Step-by-step explanation:
The fighting unit in the Macedonian army that was responsible for helping Alexander the Great defeat the Persians was the Phalanx. The Phalanx was a formation of heavily armed infantry soldiers who fought in a close formation with their shields overlapping, providing a solid wall of protection against enemies. They used long spears called sarissas to attack the enemy. This formation was highly effective in battles and was key to Alexander's military successes.
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