The Persian prince Cyrus led a rebellion against the last Median king Astyages in 553 BC. Cyrus was a grandson of Astyages and was supported by part of the Median aristocracy. By 550 BC, the rebellion was over, and Cyrus had emerged victorious, founding the Achaemenid Empire in place of the Median kingdom in the process. Croesus saw the disruption in the Median Empire and Persia as an opportunity to extend his realm and asked the oracle of Delphi whether he should attack them. The Oracle supposedly replied the famously ambiguous answer that "if Croesus was to cross the Halys he would destroy a great empire". Blind to the ambiguity of this prophecy, Croesus attacked the Persians, but was eventually defeated and Lydia fell to Cyrus. By crossing the Halys, Croesus had indeed destroyed a great empire – his own.