As far back as the eighth century BC, the ancient Greeks had invented a large, round shield, or aspis that became an essential part of warfare

Source: Ancient Greek Shields Showed Allegiance, Struck Fear Into Enemy

Opinion:

Most people interested in the ancient world realize that the Greeks have always been a colorful people. The temples and sculptures that we see today were vividly painted, not standing still in their original marble. And it seems the same holds true with their military apparatus.

I just had to post this because I thought the image of the shields, all together, was quite extraordinary!