With their bows and the superior mobility afforded by their faithful steeds, Saka Horse Archers can attack their enemies with impunity and then quickly fall back to rest and regroup. This, when combined with the Scythians' ability to train two of them at a time and Tomyris' unique ability, makes them ideal for chipping away at either powerful enemy units or city defenses. They are especially effective alongside Horsemen, which can also be trained in pairs. Even better, both units become available with Horseback Riding, making the Scythians superb rushers. Research Horseback Riding early on, secure some Horses, and raise a massive army of Saka Horse Archers and Horsemen to trample your unwary neighbors!
When facing Saka Horse Archers, your best option is to simply divide and conquer each one with multiple units of your own, using Spearmen or Pikemen if possible to exploit their vulnerability to anti-cavalry damage. Should this fail, try to bait them into easily defensible positions and chip away at their health with equal or superior units. Their range won't be enough to save them if they're outnumbered and outflanked!
The term “Saka” may refer to the Persian and Sanskrit word for the Scythians, or it may refer to a specific tribe among those horse-barbarians to the north of Assyria. Most of the confusion seems to be the ambiguous usage of Saka among the ancient “historians” – Herodotus, Strabo, Pliny the Elder, and that lot. Herodotus states that the Saka were horse archers, riding without saddles or stirrups, and distinguished by wearing quilted trousers, open tunics and “high caps tapering to a point and stiffly upright.” These horse archers were feared in the open, mostly for harassing a moving column or raiding the baggage trains, but not very good in a stand-up fight. As Alexander the Great had shown at the battle of Jaxartes (329 BC) the Saka had no staying power, and could be readily driven off by massed infantry in depth supported by ample numbers of foot archers, whose greater range and rate of fire gave them a distinct advantage over the mounted ones.