In 424BC, the forces of Athens and the Boeotian League clashed at the Battle of Delium, not far from Athens itself. The battle was a victory for the Boeotians, in part because of confusion that arose in the midst of the battle. The Athenian forces, enjoying victory, encircled a contingent of Boeotians and, unable to distinguish their shields from those of their enemies, began indiscriminately killing friend and foe alike in the first documented incident of collateral damage. The hoplite shield was a common sight, and of standardised construction since the 5th century BC. No state crests were applied to them until Sparta faced Thebes for the second time at Mantineia, in 362BC. The Thebans painted the image of a club to their shields, and likewise the Spartans emblazed a lambda (for Lacadaemonia) upon theirs. This national emblem soon became widespread and made troops distinguishable in an era where so many armies looked the same.
