The convention was constituted on the 20th of September, 1792, and commenced its deliberations on the 21st. In its first sitting it abolished royalty, and proclaimed the republic. On the 22nd, it appropriated the revolution to itself, by declaring it would not date from year IV. of Liberty; but from year I. of the French Republic. After these first measures, voted by acclamation, with a sort of rivalry in democracy and enthusiasm in the two parties, which had become divided at the close of the legislative assembly, the convention, instead of commencing its labours, gave itself up to intestine quarrels. The Girondists and the Mountain, before they established the new revolution, desired to know to which of them it was to belong, and the enormous dangers of their position did not divert them from this contest. They had more than ever to fear the efforts of Europe. Austria, Prussia, and some of the German princes having attacked France before the 10th of August, there was every reason to believe that the other sovereigns of Europe would declare against it after the fall of the monarchy, the imprisonment of the king, and the massacres of September. Within, the enemies of the revolution had increased. To the partisans of the ancient regime, of the aristocracy and clergy, were now to be added the friends of constitutional monarchy, with whom the fate of Louis XVI. was an object of earnest solicitude, and those who imagined liberty impossible without order, or under the empire of the multitude. Amidst so many obstacles and adversaries, at a moment when their strictest union was requisite, the Gironde and the Mountain attacked each other with the fiercest animosity. It is true that these two parties were wholly incompatible, and that their respective leaders could not combine, so strong and varied were the grounds of separation in their rivalry for power, and in their designs.

Events had compelled the Girondists to become republicans. It would have suited them far better to have remained constitutionalists. The integrity of their purposes, their distaste for the multitude, their aversion for violent measures, and especially the prudence which counselled them only to attempt that which seemed possible - every circumstance made this imperative upon them; but they had not been left free to remain what they at first were. They had followed the bias which led them onward to the republic, and they had gradually habituated themselves to this form of government. They now desired it ardently and sincerely, but they felt how difficult it would be to establish and consolidate it. They deemed it a great and noble thing; but they felt that the men for it were wanting. The multitude had neither the intelligence nor the virtue proper for this kind of government. The revolution effected by the constituent assembly was legitimate, still more because it was possible than because it was just; it had its constitution and its citizens. But a new revolution, which should call the lower classes to the conduct of the state, could not be durable. It would injuriously affect too many interests, and have but momentary defenders, the lower class being capable of sound action and conduct in a crisis, but not for a permanency. Yet, in consenting to this second revolution, it was this inferior class which must be looked to for support. The Girondists did not adopt this course, and they found themselves placed in a position altogether false; they lost the assistance of the constitutionalists without procuring that of the democrats; they had a hold upon neither extreme of society. Accordingly, they only formed a half party, which was soon overthrown, because it had no root. The Girondists, after the 10th of August, were, between the middle class and the multitude, what the monarchists, or the Mounier and Necker party, had been after the 24th of July, between the privileged classes and the bourgeoisie.

The Mountain, on the contrary, desired a republic of the people. The leaders of this party, annoyed at the credit of the Girondists, sought to overthrow and to supersede them. They were less intelligent, and less eloquent, but abler, more decided, and in no degree scrupulous as to means. The extremest democracy seemed to them the best of governments, and what they termed the people, that is, the lowest populace, was the object of their constant adulation, and most ardent solicitude. No party was more dangerous; most consistently it laboured for those who fought its battle.

Ever since the opening of the convention, the Girondists had occupied the right benches, and the Mountain party the summit of the left, whence the name by which they are designated. The Girondists were the strongest in the assembly; the elections in the departments had generally been in their favour. A great number of the deputies of the legislative assembly had been re-elected, and as at that time connexion effected much, the members who had been united with the deputation of the Gironde and the commune of Paris before the 10th of August, returned with the same opinions. Others came without any particular system or party, without enmities or attachments: these formed what was then called the Plaine or the Marais. This party, taking no interest in the struggles between the Gironde and the Mountain, voted with the side they considered the most just, so long as they were allowed to be moderate; that is to say, so long as they had no fears for themselves.