The Hsi-Hsia (also known as Tangutes) were a people from Central Asia that had carved out their own state from China in the year 982.
During the years 1230-32 however, Temujin's son Ogadai lead the united steppe people against the Tangutes / Hsi-Hsia. Their country was overrun, many of their villages burned down and their people enslaved. The Mongols didn't have the necessary techniques to storm their cities, though. OTOH, they managed to capture the secret of gunpowder. Ogadai wanted to take the cities by besieging them, but after two years the other Mongols thought they had a) spent enough time here and b) there wasn't enough left to loot for the effort. So Ogadai left the country for a high tribute (mostly camels). The Hsi-Hsia empire had suffered extremely under the occupation, and wouldn't recover from it.
Then in 1244 (2941, Yang Wood Dragon in the Chinese calendar), Jin China demanded from Hsi-Hsia to pay them tribute. When the Tangutes declined, the Jin decided to make war, which began in 1247 (2944, Yin Fire Sheep). In 1256 (2953, Yang Fire Dragon), Hsi-Hsia was incorporated into Jin China again, thus ending this state.