How did the french revolution change when other countries threatened to invade France to restore the monarchy?

The French Revolution became more radical when it had to face the threat of foreign invasion by neighboring monarchical powers.

King Louis XVI had been dethroned and he and his wife, queen Marie Antoinette, and their children were captives in Paris. They unsuccessfully tried to escape in 1791. War with Austria broke out, instilling false hopes in the king. Luois and the queen were accused of treason. Bourbon king Louis XVI was guillotined on January 21, 1793.

In September 1792, the National Assembly, controlled by the revolutionaries, proclaimed the First French Republic, denying hopes of a return to monarchy.