In 1226, immediately after returning from the west, Genghis Khan began a retaliatory attack on the Tanguts. His armies quickly took Heisui, Ganzhou, and Suzhou (not the Suzhou in Jiangsu province), and in the autumn he took Xiliang-fu[disambiguation needed]. One of the Tangut generals challenged the Mongols to a battle near Helan Mountains but was defeated. In November, Genghis laid siege to the Tangut city Lingzhou and crossed the Yellow River, defeating the Tangut relief army. According to legend, it was here that Genghis Khan reportedly saw a line of five stars arranged in the sky and interpreted it as an omen of his victory.