What is the relationship between politics and religion during the civil war in France during the 16th and 17th century?
During the 16th century (and into the 17th), French politics and religion were inseparably linked. Questions of religion were mixed with struggles over whose family should control the monarchy. In addition, religion was tied up with international power struggles.
During this time, two main "houses" were contending for the throne of France. These were the Bourbons and the Guise. Both families wanted to be the royal family for the sake of gaining that power. However, their conflict was also wrapped up in religion because the Bourbons were Protestant and the Guise were Catholic.
In their struggle the Guise and the Bourbons are also seen as being something of pawns of Spain and England, two of the great powers of the time. Spain and England were enemies, in part, because Spain was Catholic and England was Protestant. As part of their struggle, each of these countries tried to help "their" side win in France.
Overall, then, various factions (and outside countries) wanted power for its own sake. At the same time, they were partly motivated by religion. In this way, the relationship between politics and religion is one in which they are tangled together to the point where it's hard to tell which is more important.
Religion was closely linked to politics at that time with regards to the divine rule, whereby God decreed who was to rule as he was empowered to. Thus England and Spain, both with a dominant religion, tried to influence the course of politics in France to win the "battle" between the two religions, to define the religion in France which would define the ruler of France.