History of the Peloponnesian War

Sitalces, then, being king over all this extent of country, prepared his army to take the field. And when all was ready for him, he set out and marched against Macedonia; at first through his own dominions, then over Cercine, a desert mountain, which forms the boundary between the Sintians and Paeonians, crossing it by a road which he had himself before made, by felling the timber, when he turned his arms against the Paeonians.

In crossing this mountain from the Odrysians, they had the Paeonians on their right, and on their left the Sintians and Maedians; and after crossing it they arrived at Doberus in Paeonia.

While he was on the march, there was no diminution of his army, (except by disease,) but accessions to it; for many of the independent Thracians, though uninvited, followed him for plunder; so that the whole number is said to have been not less than one hundred and fifty thousand, of which the greater part was infantry, but about a third cavalry.

Of the cavalry the Odrysians themselves furnished the largest portion; next to them, the Getae. Of the infantry, the most warlike were those armed with swords, the independent tribe that came down from Rhodope; the rest of the mixed multitude that followed him, was far more formidable for its numbers than any thing else.