The French Wars of Religion, (1559 to 1598) were a series of conflicts fought between Catholics and Huguenots (Protestants) from the middle of the sixteenth century to the Edict of Nantes in 1598, including civil infighting as well as military operations. In addition to the religious elements, they involved a struggle for influence over the ruling of the country between the powerful House of Guise (Lorraine) and the Catholic League, on the one hand, and the House of Bourbon on the other hand.

In 1560, Catherine de Medici became regent for her young son Charles IX. Her inexperience and lack of financial support created a "political vacuum" and Catherine felt that she had to steer the throne carefully between the powerful and conflicting interests that surrounded it. Although she was a sincere Roman Catholic, she was prepared to deal favourably with the Huguenot House of Bourbon in order to have a counterweight against the overmighty House of Guise. She nominated a moderate chancellor, Michel de l'Hôpital, who urged a number of measures providing for toleration of the Huguenots.

She therefore was led to support religious toleration in the shape of the Edict of Saint-Germain (1562), which allowed the Huguenots to worship publicly outside of towns and privately in towns. On March 1, however, a Guise-led faction attacked a Huguenot service at Wassy-sur-Blaise in Champagne massacring the innocent worshippers there. The Edict was revoked, under pressure from the Guise faction.

This provoked the First War.The Bourbons, led by Louis I de Bourbon, Prince de Condé, organised a kind of protectorate over the Protestant churches and began to garrison strategic towns along the Loire. Here, at Battle of Dreux and at Orléans, there were the first major engagements; at Dreux, Condé was captured by the Guises and Montmorency, the government general, by the Bourbons. In February 1563, at Orléans, Francis, Duke of Guise was assassinated, and Catherine's fears that the war might drag on led her to negotiate a truce and the Edict of Amboise (1563).

This was generally regarded as unsatisfactory by all concerned, the Catholics in particular being uneasy about what they regarded as unwise concessions to the heretics. The political temperature of the surrounding lands was rising, as unrest grew in the Netherlands. The Huguenots became suspicious of Spanish intentions when the latter reinforced their strategic corridor from Italy north along the Rhine and made an unsuccessful attempt at taking control of the king. This provoked a further outburst of hostilities (the Second War) which ended in another unsatisfactory truce, the Peace of Longjumeau (March 1568).

In September of that year, war again broke out (the Third War). Catherine and Charles decided to throw in their lot with the Guises. Religious toleration was once more at an end, and the Huguenot army, under the command of Louis I de Bourbon, prince de Condé and aided by forces from south-eastern France led by Paul de Mouvans and a contingent of fellow Protestant militias from Germany — including 14,000 mercenary reiters led first by the Duke of Zweibrücken, who was killed in combat and then succeeded by the Count of Mansfeld — and from the Netherlands, led by William of Orange and his brothers Louis and Henry, and co-financed by Elizabeth of England [3] fought the Catholics, who were led by the Duke d'Anjou (future Henry III) and assisted by troops from Spain, the Pope and the Duke of Tuscany.

Source : http://en.wikipedia.org