In 1603 a man calling himself Dmitri-first of the so-called False Dmitris-and professing to be the rightful heir to the throne, appeared in the Polish-Lithuanian Commonwealth.
A few months later in 1603, Polish forces crossed the frontier with a small force of 4,000 Poles, Lithuanians, Russian exiles, German mercenaries and Cossacks from the Dnieper and the Don, in what marked the beginning of the Polish Commonwealth's intervention in Russia, or the Dymitriad wars.