Initially the first hussar units in the Kingdom of Poland were formed by the Sejm (Polish parliament) in 1503, which hired three banners of Hungarian mercenaries. Soon, recruitment also began among Polish citizens. Being far more expendable than the heavily armoured lancers of the Renaissance, the Serbian-Hungarian hussars played a fairly minor role in the Polish Crown victories during the early 16th century, exemplified by the victories at Orsza (1514) and Obertyn (1531). During the so-called "transition period" of the mid-16th-century, heavy hussars largely replaced armoured lancers riding armoured horses, in the Polish "Obrona Potoczna" cavalry forces serving on the southern frontier.