The invasion began in late 1259, after a powerful Mongol army had been sent to the Kingdom of Galicia–Volhynia in order to punish King Daniel of Galicia for his independent actions. King Daniel had to comply to Mongol demands, and in 1258, his forces joined the Mongols in the raid on the Grand Duchy of Lithuania. To weaken Daniel's position, the Golden Horde decided to attack his allies, Hungarian KingBéla IV, and Duke of Kraków, Bolesław V the Chaste. The purpose of the invasion was to loot the divided Kingdom of Poland, and to weaken Duke of Kraków Bolesław V the Chaste, whose province, Lesser Poland, began a process of fast development. According to the Mongol plan, the invaders were to enter Lesser Poland east of Lublin, and head towards Zawichost. After crossing the Vistula, the Mongol army was to break into two columns, operating north and south of the Holy Cross Mountains. The columns were to unite near Chęciny, and then head southwards, to Kraków. Altogether, Mongol forces under Boroldai were 30,000 strong, with Ruthenian units of King Daniel of Galicia, his brother Vasilko Romanovich, Kipchaks and probably Lithuanians or Yotvingians. The events that took place in the Kingdom of Galicia–Volhynia echoed in Lesser Poland, and in late 1258, preparations for the defence of Kraków began. The work was quickly abandoned, and Piast dynasty dukes returned to their internal quarrels. In October 1259, right before the invasion, Duke of Greater PolandBolesław the Pious allied himself with Duke Bolesław V the Chaste and Duke of MazoviaSiemowit I, in order to attack Duke of Kujawy, Casimir I of Kuyavia. A few weeks later, Lesser Poland was invaded by the Mongol hordes. The Mongolian army concentrated near Chełm, and after capturing Polish towns east of the Vistula, the invaders appeared at Sandomierz. Boroldai ordered Ruthenian auxiliary units to besiege and capture the city, while main Mongol forces marched westwards toward the Holy Cross Mountains. Their march was marked by an orgy of destruction; among others, ancient abbeys of Koprzywnica and Wąchock were looted. The Mongols limited their advance to Radom in the north and Sulejów in the west, and did not enter other Polish provinces. The two columns of the invading army joined forces near Kielce and Chęciny, in mid-January 1260. At the same time, the siege of Sandomierz continued. Defenders of the city fiercely resisted all attacks of the Mongol and Ruthenian forces. After several weeks, Mongol leaders began negotiations with the Poles, who were commanded by a man named Piotr of Krepa. Ruthenian princes, which took part in the siege, advised Piotr of Krepa to accept Mongol offers, and abandon Sandomierz, in exchange of safe passage for all residents of the city. Finally, facing hunger and epidemics, the Poles left Sandomierz on February 2, 1260; the Mongols broke their promise and massacred the civilians and the defenders. The city itself was looted and burned to the ground. On February 5, main Mongol forces abandoned Sandomierz. All units joined forces on February 10–12, and entered densely populated southern Lesser Poland. After looting the abbeys at Jędrzejów, Mogila, Szczyrzyc and Miechów, the invaders flooded the region in an orgy of murder and destruction. In the second half of February, the Mongols reached Kraków, quickly capturing the city, but without the Wawel Hill, which was fortified and defended. To prevent Silesian Piast dukes from sending their support to Lesser Poland, Boroldai sent some units to the area of Bytom. Duke Bolesław V the Chaste himself fled to Sieradz, with his wife Kinga of Poland. In late March 1260, the Mongols left Lesser Poland eastward along the Carpathian foothills.
Aftermath
The province that they had invaded was completely destroyed with rich loot taken. Some 10,000 Poles were taken with the invaders as slaves. The success of the Golden Horde was complete, as they managed to destroy an anti-Mongol alliance, and completely subjugate the Kingdom of Galicia–Volhynia.
