King Sigmond did more than that. He summoned Mihaly to his court and made him a royal squire. Mihaly moved up the ranks quickly becoming the Court Chamberlain in 1433. In that same year he accompanied the king to Rome where the pope crowned Sigismund as Holy Roman Emperor. He was still a young man in his 20s when he became the Royal Treasurer in1436.
Although the Guthy family was prestigious in terms of lineage, by Mihaly's time they had become impoverished members of the lesser nobility. He raised the family up to the highest level of the aristocracy, to barons of the realm who were addressed with the prefix 'magnificus.'
Although he excelled in political spheres Mihaly was also a knight with strong military abilities as well.
He fought with John Hunyady on the winning side of the civil war that followed the death of King Sigmond at the end of 1437. In 1445 Mihaly became one of the seven Captains of the Realm elected to govern the kingdom until the heir to the throne, Ladislaus II, who was not only a child but also held captive in Austria by Frederick III , could be crowned king. The seven captains in turn elected John Hunyady, who had become a national hero for his successful battles against the Turks, as Captain General of the Realm.
Mihaly was serving as commander of Belgrade Castle when the Ottoman Empire under Sultan Mehmed, in an attempt to invade Hungary, attacked the fortress with a force of 80,000- 100,000 soldiers. All Europe awaited the outcome anxiously. Mihaly only had about 2,000 men to defend the fortress. Luckily he was joined by his old friend, John Hunyady and his army of 20,000 men, half of them armed peasants and tradesmen rallied by a crusade preaching Franciscan monk. Together they managed not only to defend Belgrade but they pulled off a miraculous victory, routing the Turks and chasing them out of the kingdom. Pope Callixtus III ordered all of Christendom to pray for the defenders of Belgrade and that all the church bells in Europe ring out at noon in thier honor, a tradition that lasts to this day. John Hunyady died in the aftermath of the battle. No doubt, Mihaly was by his side.
- Eve Hars