On June 24th, 1386, Saint John was born in the village of Capestrano in the Kingdom of Naples. His father was a former Germanic Knight and had come to Italy with the Angevin court of Louis I of Anjou. After an early education, Saint John studied law at the University of Perugia (one of the free universities of Italy, Pope Clement V elevated it to a stadium generale in 1308. In 1355 it was elevated to the rank of Imperial University by the Emperor Charles IV). After graduation, he practiced law in the courts of Naples.
King Ladislaus of Naples appointed Saint John the Governor of Perugia in 1412 and he was sent as an ambassador to Malatestas in 1416 when the two states engaged in war. Malatesta did not welcome him as an ambassador - instead Saint John was arrested and placed into a jail cell for the remainder of the war. It was during this time of imprisonment that he began to seriously contemplate the fate of his soul and experienced a vision of Saint Francis asking him to join the Franciscan Order. Once freed from the prison, he joined the Order of Friars Minor at Perugia (along with James of the Marches) on October 4th, 1416. They studied theology under Saint Bernardine of Siena.
After his ordination in 1425 he began travelling Europe preaching repentance. He travelled through Italy, Germany, Bohemia, Austria, Hungary, Poland and even as far as Russia drawing massive crowds. At one sermon preached in the town of Brescia Italy, the crowd was estimated at over 126,000 people. Another time, as his fame as a healer spread, a crowd of 2,000 people were brought to him, seeking his blessing through the sign of the cross to heal their illnesses.
When not actively preaching, he helped propagate devotion to the Holy Name of Jesus and engaged heavily with Saint Bernardine in the reform of the Franciscan order. The two saints were promoting a return to a more strict discipline for members within the order. Many of his writings during this time were theories of Papal supremacy over councils and along side Saint Bernardine, Saint James of the Marche and Saint Albert Berdini of Sarteano are considered the four great pillars of the Observant reform in the Friars Minor. These reforms and devotions to the Holy Name of Jesus led both Saint John and Saint Bernardine to be accused of heresy. In 1429, Saint John and the other Observant friars were formally cited to Rome on charges of heresy. The companions chose Saint John to defend their cause and were eventually acquitted by the commission of Cardinals.
Over the next few years the Papacy sent Saint John on several embassy missions : in 1439 he was sent as a legate to Milan and Burgundy to oppose the Antipope Felix V, in 1446 he was sent on behalf of the Vatican to the King of France, and in 1451 sent as Apostolic Nuncio to Austria. He combatted the heresy of the Hussites and prosecuted the last Fraticelli of Ferrara.
In 1453, the great city of Constantinople fell to the Ottoman Empire (under Sultan Mehmed II) and all of Christian Europe was now threatened by the Empire. Pope Callixtus III in 1454 sent Saint John (by now aged 70) to preach a Crusade at the Imperial Diet of Frankfurt. After little success and almost no response in Austria, he instead left for Hungary where he gathered a large army to help relieve the siege of Belgrade. In the summer of the same year, that army, led by John Hunyadi broke the siege of Belgrade and forced the Turkish army to retreat. Saint John himself led a contingent of troops into the fray (specifically on the left wing of the army), earning him the title "Soldier Priest".
After the battle, Saint John fell ill at the town of Ilok with the bubonic plague. He succumbed to the plague on October 23rd, 1456. Saint John of Capistrano was beatified in 1694 by Pope Alexander VIII and canonized in 1724 by Pope Benedict XIII. His original feast day fell on March 28th (in 1890) but was moved to October 23rd in 1969 by Saint Pope Paul VI. Due to his actions at the battle he often listed as the patron Saint of Military Chaplains.