It was the Duke of Bavaria, Charles Albert, who succeeded Maria Theresa's father Charles VI as Holy Roman Emperor, breaking the Habsburg succession streak that had started fifty years before Columbus discovered America.
Charles Albert, a Prince-Elector of the Holy Roman Empire, had a very good claim to becoming Emperor over his cousin Maria Theresa's husband, Francis Stephen.
Charles Albert was also the son-in-law of a Holy Roman Emperor, Joseph I, who himself was a Habsburg.
Joseph I was Charles VI's older brother and had actually preceded Maria Theresa's father as Emperor.
Charles Albert's great-great-grandfather was Habsburg Emperor Ferdinand II, just as was the case for Maria Theresa, whereas Francis Stephen was Ferdinand II's great-grandson.
The biggest difference came down to the Pragmatic Sanction of 1713, which allowed Maria Theresa to inherit the Habsburg kingdoms and prohibited dividing those lands and thereby diluting the Habsburg holdings.
Charles Albert never signed the Pragmatic Sanction of 1713, because he realized it edged out his claims to Habsburg kingdoms in favor of Maria Theresa and her husband Francis Stephen.
Emperor Charles VI had spent his lifetime gathering signatures for the document that allowed Archduchess Maria Theresa to inherit his kingdoms, undivided, but in fact he had years earlier signed a contradictory Mutual Pact of Succession written by his father, Emperor Leopold I, when the senior line of the House of Habsburg, King Charles II of Spain, died without a direct male heir.
That Mutual Pact of Succession specifically gave the heirs of Joseph I, not Charles VI, precedence in claims to the family leadership if neither had a son.
Shortly after Charles VII's coronation as Holy Roman Emperor, Maria Theresa's Austrian troops, now revitalized under her firm, resolved leadership, counterattacked to capture most of his Bavarian holdings.
In short, Charles VII and his allies had overplayed their hands, expecting Maria Theresa to fold, but she drew to her own strengths instead.
While militaristic Prussia fielded an impressive army roughly equal in size to that of the Austrians at the time Maria Theresa came to the throne, Austria was a much larger country with far greater resources.
Prussia itself had 2 million citizens versus 16 million in Austria.
In addition, as mentioned earlier, Hungary had sent 60,000 troops to supplement Austria's 82,000 soldiers.
While France was also a powerful ally to Charles VII, the French motivation was primarily to cause trouble for Great Britain's allies so as to weaken their long time enemy elsewhere.
Great Britain's King George II, however, was actually born and raised in northern Germany and was also a Prince-Elector of the Holy Roman Empire, so he wasn't going to just sit idly by and let the future of Europe be decided without him.
Realizing French power would increase if Maria Theresa lost power, King George II not only sided with Austria diplomatically but actually sent troops and personally commanded an Anglo-Allied army to help turn the tide.
However, in late 1744 Prussia and France managed to reclaim Bavaria for Emperor Charles VII.
In a rapid twist, Charles VII died three months later at the age of 47, and Maria Theresa's husband Francis Stephen succeeded him as Holy Roman Emperor nine months after that, taking the name Francis I.
As the War of Austrian Succession continued, France became involved in attempting to remove King George II from the British throne by assisting the Jacobite movement to re-instate the Stuart line in Great Britain and crown Bonnie Prince Charlie as their King.
This pulled King George II's attention back to his homeland.
By 1748, France and England decided to resolve a lot of their spats all over the world with the Treaty of Aix-la-Chapelle, which among other things confirmed King George II's House of Hanover succession in both the UK and Germany and allowed Maria Theresa to keep most of her Habsburg holdings, but notably allowing Prussia to keep Silesia.
Maria Theresa would continue to refer to Frederick the Great of Prussia as "that evil man," but the reason France and England allowed Prussia to keep Silesia was the realization that Prussia could be a powerful ally, so neither wanted to be the one to antagonize Frederick by taking away his conquest. Perhaps more to the point, at the outset of the War, Frederick had offered to recognize Maria Theresa as legitimate heir to the House of Habsburg if she would let Prussia keep Silesia.
Nonetheless, just as in the twentieth century's World Wars I and II, Great Britain's side clearly won in Europe, which must have made the unexpected loss to their American colonies 35 years later all the more shocking.
Within a few years after the Treaty of Aix-la-Chapelle, America would become a major battleground for France and Great Britain in the French and Indian War, during which young colonial George Washington gained battle experience as a British officer.
In Central Europe, however, Empress Maria Theresa had successfully reclaimed what she considered her family line's rightful position, which she would pass on to her children, two of whom would go on to become Holy Roman Emperors.