Skirmishers possess a strong ranged attack and an increased movement rate, allowing them to perform hit and run attacks.
Skirmishers are fast ranged units, deadly on open terrain. Unlike the Chariot before them, they can move through rough terrain without a movement penalty. As a mounted unit, the Skirmisher is vulnerable to units equipped with spears.
In the 12th century, nomadic tribes came boiling out of Central Asia, conquering most of Asia, Eastern Europe and a large portion of the Middle East within a century. Their primary weapon was their incomparable mounted bowmen. The Mongols were one such nomadic tribe, and their children were almost literally "raised in the saddle." Riding on their small but hearty steppe ponies, the lightly-armed and armored Mongol Keshiks, a type of skirmisher, could cover an astonishing amount of territory in a day, far outpacing any infantry or even the heavier European cavalry.
In battle the Mongol Keshiks would shoot from horseback with deadly accuracy, disrupting and demoralizing the enemy formations. Once the enemy was suitably weakened, the Mongol heavy cavalry units would charge into the wavering foe to deliver the coup de grace. When facing armored European knights the Mongols would simply shoot their horses, then ignore or destroy the unhorsed men as they wished.