The Champ de Mars Massacre takes place on July 17, 1791, in Paris in the midst of the French Revolution.

The event is named after the site of the massacre, the Champ de Mars.

Two days before, the National Constituent Assembly had issued a decree that the king, Louis XVI, would remain king under a constitutional monarchy.

This decision had come after King Louis XVI and his family had unsuccessfully tried to flee France in the Flight to Varennes the month before.

Later that day, leaders of the republicans in France rally against this decision, eventually leading royalist Lafayette to order the massacre.

Jacques Pierre Brissot, editor and main writer of Le Patriote français and president of the Comité des Recherches of Paris, draws up a petition demanding the removal of the king.

A crowd of fifty thousand people gathers at the Champ de Mars on July 17 to sign the petition, with about six thousand having signed the petition.

However, earlier that day two suspicious people had been found hiding at the Champ de Mars, "possibly with the intention of getting a better view of the ladies' ankles", and are hanged by those who found them.

Jean Sylvain Bailly, the mayor of Paris, uses this incident to declare martial law.

The Marquis de Lafayette and the National Guard, which is under his command, are able to disperse the crowd.

Later in the afternoon, the crowd, led by Danton and Camille Desmoulins, returns in even greater numbers.

The larger crowd is also more determined than the first.

Lafayette again tries to disperse it.

In retaliation, the crowd throws stones at the National Guard.

After firing unsuccessful warning shots, the National Guard opens fire directly on the crowd.

The exact numbers of dead and wounded are unknown; estimates range from a dozen to fifty dead.