Joan of Arc
Sixteen year old illiterate peasant girl with no military background convinces a bunch of knights to escort her through hundreds of miles of enemy territory to go talk to the future King of France, Charles VII and convince him that she needs command of the army so she can beat the hell out of the English because God told her to do it.
Note that at this time it's been about a hundred years into the Hundred Years' War and France has not won a major victory. All the fighting happens on French soil and a large portion of France is under English control. Including Paris, the capital and Reims where Charles needs to get crowned despite the fact that the Treaty of Troyes gave the French crown to Henry IV's descendants.
So, Joan sneaks thru English lines and impresses Charles enough in her job interview that he sends her to lead the army that's being sent to break the English siege of Orleans. Orleans being a point of great importance and the loss of the city would probably have lead to the collapse of the French resistance.
Joan gets there and despite not being included in war councils at first and lots of executive meddling convinces the French to adopt a new aggressive strategy. When the guys who are supposedly under her drag their feet, she goes off by herself with a few of the common soldiers and captures a fort.
Also on the final assault against the largest nearby English fortress, she gets shot in the neck by a crossbow bolt. And then resumes doing what she was doing, leading the charge into a fortified enemy position to kill people.
After this she gains more support and her staff drag their feet less. The French beat the English down in a number of other battles and then capture Reims, deep in enemy territory (her idea) and Charles gets crowned.
She gets captured in a skirmish defending Compiegne because she orders a retreat and insists on being the last one to leave.
At this time, because of politics, Charles drags his feet in ransoming her back and she gets sold to the English by the Burgundians who captured her. The English having already decided that she needs to die because they're getting the hell beaten out of her.
Not being one to sit around, Joan tries to escape. By jumping out of this tower they locked her in.
This tower is seventy feet tall by the way. The English, realizing that Joan is not bothered by things that kill normal people (crossbow bolts to the neck, falling from great heights, leading charges into fortified positioins, etc.) decide that they should accuse her of being a witch and try to kill her with fire. Then they locked her up somewhere else with soldiers watching her constantly.
But for this sort of thing you need a trial. Joan was smart enough to realize that they were stacking the cards against her. She was denied counsel. Assuming that it would be easy to cross up and humiliate an illiterate peasant girl, they decided to hold her sessions in public.
Except she crossed them up instead. Asked if she knew she was in God's grace, she answered: 'If I am not, may God put me there; and if I am, may God so keep me.'" The question is a scholarly trap (Joan doesn't care). Church doctrine held that no one could be certain of being in God's grace. If she had answered yes, then she would have convicted herself of heresy. If she had answered no, then she would have confessed her own guilt. The moment the court heard this reply, "Those who were interrogating her were stupefied."
Being fairly pissed off at not being able to win a game they created against an illiterate peasant girl the British nonetheless eventually found some sort of excuse to have her burned. They burned her thrice. You know. Just to make sure she was dead.
A couple hundred years later she became a Saint. Also she's the national hero of France.