He was his father's fourth son. However, two of his elder brothers had died in infancy while Ferdinand, the eldest, was intended to inherit the Imperial Crown. However, Ferdinand died when only almost twenty-one years old, followed three later by their father, Emperor Ferdinand III. As a result, Leopold became Emperor when barely eighteen years old. 
The French had tried to dispute his rights as they regarded him as stupid and dim-witted. Leopold was indeed shortsighted, ugly and undersized, with his teeth broken by scurvy. As well, he was shy and had wanted to enter the church. However, he was called to lead Austria which, still recovering from the Thirty Years' War, was besieged by the arrogant French on one side and the Ottoman Turks on the other. He made mistakes, alienated the Protestants in Hungary, and hid himself from the world behind a barrier of protocol and etiquette taken from the Spanish Court. However, he could be gay and charming. He composed music and played several musical instruments. He loved books and painting and was also an alchemist. 
His first wife, Infanta Margarete of Spain, was the daughter of his own elder sister. However, she died aged only twenty-one after the birth of their fourth child. 
His second wife also died young, having given birth to two short-lived daughters. However, his third wife, Eleonore Magdalene, was to survive him by almost fifteen years, having borne him ten children. At first he had left decision-making to his ministers until, finding himself betrayed, he took the government into his own hands. He had the qualities for survival, especially when he had to defend 
himself alone against both Louis XIV of France and the Sultan at the same time. However, once joined by King William III of England, he survived with the genius of the Duke of Marlborough and Prince Eugene of Savoy. 
Leopold I, a bigot and lacking imagination, drove the Hungarians to rebellion yet still survived. In 1683 a great army of Turks attacked his Empire, laying siege to Vienna. The Turks burned and massacred in cold blood. Fearing his capture would demoralize the country, Leopold I left Vienna in advance and called an Imperial Diet at Regensburg. He then gathered an army and was joined by Johan 
Sobieski, King of Poland. 
Count Starhemberg had reinforced Vienna and drilled the citizens into an auxiliary army. University students would make night-time forays and bring back prisoners as well as food and cattle stolen from the Turks. However, after three months of bombardment and with a population on the edge of starvation, a breach was at last made in the walls of Vienna. After five days of desperate fighting the end seemed near; but then Johan Sobieski arrived and, with his Poles, rescued 
Vienna and the Empire. 
Emperor Leopold I soon arrived by boat from Linz. Sobieski and Charles of Lorraine pursued the Turks and the fighting against them was to last for many years. Meanwhile, Leopold I had returned to be regarded the saviour of Europe. In the process of recovery, the arts flourished and he founded Universities and Libraries. On the other hand he would not allow the Jesuits to educate his children. He may have seemed slow, but he had a tough and enquiring mind. A practical man, he reformed the legal system and established a regular police 
force. He also organised a proper army so that he was able to dispense with the mercenary armies. His best support was from Prince Eugene of Savoy, a great soldier and wise councillor. When Leopold died a year after the victory at Blenheim, he left a standing army of 74,000 men and a secure Empire.

Source: Leo van de Pas