Zizka's name first became prominent when the Hussite movement began. When in 1419 a Hussite procession was stoned at Prague from the town hall, Zizka headed those who threw the town councillors from its windows. When a temporary armistice was concluded between the partisans of King Sigismund and the citizens of Prague, Zizka marched to Plzen with his followers, but soon left that city, and, after defeating at Sudomer the partisans of Sigismund, arrived at Tabor, the newly founded stronghold of the advanced Hussites.
Zizka took a large part in the organization of the new military community and became one of the four captains of the people (hejtman) who were at its head. Meanwhile Sigismund, king of the Germans and king of Hungary, invaded Bohemia, claiming the crown as the heir of his brother Wenceslaus. Menaced by Sigismund, the citizens of Prague entreated the Taborites for assistance. Led by Zizka and their other captains, the Taborites set out to take part in the defence of the capital. At Prague Zizka, and his men took up a strong position on the hill then known as the Vitkov, on the spot where Zizkov, a district of Prague, now stands. At the end of June 1420 the siege of the city began, and on July 14 the armies of Sigismund made a general attack. A strong German force assaulted the position on the Vitkov which secured the Hussite communications with the open country. Mainly through the heroism of Zizka, the attack was repulsed, and the forces of Sigismund abandoned the siege. (A huge monument was erected on the top of the hill to honor Jan Zizka. The statue has Zizka sitting on the largest horse statue in the world. It is 9 meters or over 27 feet tall.) Shortly afterwards (August 22, 1420) the Taborites left Prague and returned to Tabor.
Zizka was now engaged in constant warfare with the partisans of Sigismund, particularly with the powerful Romanist, Ulrich of Rosenberg. By this struggle, in which Zizka was invariably successful, the Hussites obtained possession of the greatest part of Bohemia, which Sigismund now left for a time. It was proposed to elect a Polish prince to the throne; but meanwhile the estates of Bohemia and Moravia, who met at Caslav on June 1, 1421, decided to appoint a provisional government, consisting of twenty members chosen from all the political and religious parties of the country, Zizka, who took part in the deliberations at Caslav, being elected as one of the two representatives of Tabor.
Zizka summarily suppressed some disturbances on the part of a fanatical sect called the Adamites. He continued his campaigns against the Romanists and adherents of Sigismund; and having captured a small castle near Litomerice he retained possession of it, the only reward for his great services that he ever received or claimed. According to the Hussite custom he gave the biblical name of Chalice to this new possession, and henceforth adopted the signature of Zizka of the Chalice. Later, in 1421, he was severely wounded while besieging the castle of Rabi, and lost the use of his remaining eye. Though now totally blind, he continued to command the armies of Tabor.
At the end of 1421 Sigismund, again attempting to subdue Bohemia, obtained possession of the important town of Kutna Hora. Zizka, who was at the head of the united armies of Tabor and Prague, at first retreated to Kolin, but after having received reinforcements he attacked and defeated Sigismund's army at the village of Nebovidy between Kolin and Kutna Hora (January 6, 1422). Sigismund lost 12,000 men and only escaped himself by rapid flight. Sigismund's forces made a last stand at Nemecky Brod (Deutschbrod) on the 10th of January, but the city was stormed by the Czechs, and, contrary to Zizka's orders, its defenders were put to the sword.
Early in 1423 internal dissensions among the Hussites led to civil war. Zizka, as leader of the Taborites, defeated the men of Prague and the Utraquist nobles at Horice on April 20, but shortly afterwards the news that a new crusade against Bohemia was being prepared, induced the Hussites to conclude an armistice at Konopiste on June 24, 1425. As soon, however, as the so-called crusaders had dispersed without even attempting to enter Bohemia, the internal dissensions broke out afresh. During his temporary rule over Bohemia Prince Sigismund Korybutovic of Poland had appointed as governor of the city of Hradec Kralove Borek, lord of Miletinek, who belonged to the moderate Hussite, the so-called Utraquist, party. After the departure of the Polish prince the city of Hradec Kralove, in which the democratic party now obtained the upper hand, refused to recognize Borek as its ruler, and called Zizka to its aid. He acceded to the demand and defeated the Utraquists under Borek at the farm of Strachov, near the city of Hradec Kralove (August 4, 1423).
Zizka now attempted to invade Hungary, which was under the rule of his old enemy King Sigismund. Though this Hungarian campaign was unsuccessful owing to the great superiority of the Hungarians, it ranks among the greatest military exploits of Zizka., on account of the skill he displayed in retreat. In 1424, civil war having again broken out in Bohemia, Zizka decisively defeated the Praguers and Utraquist nobles at Skalice on January 6, and at Malesov on June 7. In September he marched on Prague, but on the 14th of that month peace was concluded between the Hussite parties through the influence of John of Rokycany, afterwards Utraquist archbishop of Prague. It was agreed that the now reunited Hussites should attack Moravia, part of which country was still held by Sigismund's partisans, and that Zizka should be the leader in this campaign. But he died of the plague at Pribyslav (October 11, 1424) before reaching the Moravian frontier.