How did persia rise from nomadic roots to become the largest land empire the work had ever seen?

Persia’s rise to power began with the marriage between a Persian and a Median. Cyrus, the son of a powerful Persian chief, married a Median princess. The Medes had been the first to achieve a complex political organization in Central Asia near western Iran. The Persians eventually overthrew the Median monarch but maintained the framework of the Median government. I hope that helps :)