Did the executution of the king advence the goals of the revolution or was it a setback?

Answer 1

What we tend to forget about the French Revolution is that, in its early stages, it wasn't run by a bunch of extremist Jacobins who wanted to cut everyone's head off. The National Assembly that effectively took power from the Estates General after the Tennis Court Oath of June 20, 1789, was a relatively moderate body that wanted a constitutional monarchy, including a king (Louis XVI) and a court that would be placed under much more moderate limitations than they were used to. The fact that Louis never really committed himself to the new regime, and in fact sent increasingly desperate pleas to his neighbors asking for help to save him and his family from his own people, was just one of the many factors that moved popular opinion from the moderates in the centre of the Assembly to the extremists on the left. (By the way, the terms right-wing and left-wing originate from the factions in the house at Versailles before the move back to Paris.)

When the Duke of Brunswick issued his ultimatum to the people of Paris, demanding the release of the king and his family, that pretty much sealed the fate of the king, because it was clear that Louis had himself been fomenting for exactly this sort of foreign intervention. The National Guard, which had at first been singularly ineffective in fighting the incursions of several hostile neighbors, coalesced into a patriotic organization that began to gain some advantages on the battlefields.

By the time the Convention was in place and the details of Louis' machinations with foreign powers were publicized, it was inevitable that he would be brought to trial and convicted. The only question was whether he would be executed or imprisoned. Ironically, the same group of people who had been adamantly against capital punishment a few short years earlier--the Jacobins--were now equally adamant that the enemies of the people should pay with their lives. In retrospect, it's obvious that keeping Louis alive as a prisoner would only have made him a hostage that would be hotly attractive to any group or army or state that wanted to put him back on the throne for its own particular ends. The Convention had no choice, really, except to call for Louis' execution. As Robespierre famously said, "Either he dies or the Revolution dies" (or something to that effect).

Now, finally, to the question. When the revolutionary government executed the man who was only, technically, Citoyen Louis Capet, it was effectively committing itself to hard-line action against any and all counter-revolutionaries and planting itself firmly in support of a rational Republican government. Although a great many of the French people were aghast at the thought of executing God's anointed, there were many more who recognized the necessity of putting the old regime permanently aside and focusing on saving the nation of France--the new republic--from its enemies, internal and external. Unfortunately, this witch hunt for traitors eventually descended into the Terror later that year, but it's a mistake to make a direct connection between Louis' execution and the madness of the Terror: the former was a political necessity; the latter was extremism by paranoid elements that got control of the Convention from men who should have been making the rational decisions.

Louis' execution was, in the final analysis, a furtherance of revolutionary goals because it made a clear statement that no one, not even the king--especially not even the king--was above the law of the land that protected all the people from the excessive intervention of its own government. Treason is treason and that's that.