In 1559, Francis II ascended to the throne of France. Poor, poor Francis was only 15 at the time, and you really can't expect a teenage monarch to think on his own - whoever advises the young King will, for all intents and purposes, rule France. Three political families were working on bending Francis's ear their way - the Guises, the Bourbons, and the Montmorency-Chatillons. The Guises won out in the early going, controlling Francis like a puppet, until someone else cut the strings - Francis II died in 1560.

Charles IX came into power, but he was even younger. The rule of regency took effect, and his mother, Catherine de Medici, became the protector of France. Her first moves here against the powerful Guise house - Catherine allowed the Protestants of France at the time, the Huguenots, to worship publicly. You see, the Guises were in tight with the Catholic Church, and the Bourbons and Montmorency-Chatillons controlled more Protestant lands. So, Catherine took the 'enemy of my enemy is my friend' approach. She franchised the Huguenots, therefore bolstering the political power of the anti-Guise factions. The Duke of Guise was not amused at this heretical action.

In March of 1562, the Duke of Guise whipped his forces together and descended on a Protestant service in Champagne. All worshippers were killed; estimates range from 100 to 1,000 dead. The Bourbons and the Montmorency-Chatillons declared war.

Catherine de Medici consulted her 'Ruling France... for Dummies' book (inspired by this Machiavelli guy, apparently) and decided that if the three families were too caught up in killing one another, they would forget all about her, and she could rule in peace. She set about on keeping the families at each other's throats, which by and large worked, until August 1572.

A member of the Montmorency-Chatillon family, Gaspard de Coligny, was a major leader of the Huguenot movement in France. Naturally, he was a marked man from the get-go, and someone finally succeeded in shooting him in August 1572. Coligny lived; he became convinced that the assassination attempt was commissioned by Catherine; he convinced his followers that Catherine de Medici and the Guises were in on it together.

Catherine struck back, convincing Charles that the Huguenots were at the gates, demanding his head on a platter. And Charles did what he felt he had to do, to protect his regency - he sent out the royal troops and killed all the Huguenots in Paris, hunting down each and every last Protestant soul that wasn't fast enough to split town. 3,000 Huguenots died in this, called the St. Bartholomew's Day Massacre, and up until the 20th century, it was the largest systematic killing of non-combatants known.

By the way : this was, in a nutshell, the first 10 years of the French Religious Wars.