Joseph continued the War of the Spanish Succession, begun by his father against Louis XIV of France, in a fruitless attempt to make his younger brother Charles (later Emperor Charles VI) King of Spain. In the process, however, owing to the victories won by his military commander, Prince Eugene of Savoy, he did succeed in establishing Austrian hegemony over Italy. Joseph also had to contend with a protracted revolt in Hungary, fomented by Louis XIV. Neither conflict was resolved until after his death.
His motto was Amore et Timore (Latin for "Through Love and Fear").
Born in Vienna, Joseph was educated strictly by Prince Dietrich Otto von Salm and became a good linguist. Although he was the first son and child born of his parents' marriage, he was his father's third son and seventh child. Previously, Leopold had been married to Infanta Margaret Theresa of Spain, who had given him four children, one of whom survived infancy. He then married Claudia Felicitas of Austria, who gave him two short-lived daughters. Thus, Joseph had six half-siblings. In 1684, the six-year-old Archduke had his first portrait painted by Benjamin Block. At the age of nine, on 9 December 1687, he was crowned King of Hungary; and at the age of eleven, on 23 January 1690, King of the Romans. Although he never formally ceased to be a Roman Catholic, Joseph (unlike his parents and most of his other relatives) was not particularly devout by nature. He had two great enthusiasms: music and hunting.
Prior to his ascension, Joseph had surrounded himself with reform-hungry advisors and the ‘young court’ of Vienna was ambitious in the elaboration of innovative plans. He was described as a "forward-looking ruler". The large number of privy councillors was reduced and attempts were made to make the bureaucracy more efficient. Measures were taken to modernize the central bodies and a certain success was achieved in stabilizing the chronic Habsburg finances. Joseph also endeavoured to strengthen his position in the Holy Roman Empire – as a means of strengthening Austria’s standing as a great power. When he sought to lay claim to imperial rights in Italy and gain territories for the Habsburgs, he even risked a military conflict with the Pope over the duchy of Mantua.