After the Persian War, what did Sparta, Athens, and other Greek communities collect to
ward off future external attacks?

They collected resources for building walls.

Explanation:

Building walls would help keep intruders out.

ww1 weapons: tank. tanks were used for the first time in the first world war at the battle of the somme. they were developed to cope with the conditions on the western front. the first tank was called 'little willie' and needed a crew of 3.