The Answer is:
Alexander’s troops had much protection on their head and chest. This could be because their troops were more valuable and not as replaceable as the Romans who also had protective armor but not as heavy. The Romans carried more light armor for better mobility. To the Romans speed was more important than defense. They did not fight like a unit as much as the Alexandrians did, it was more stagnant and vicious.
Step-by-step explanation:
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