France declared war on Britain in February 1793. Wollstonecraft tried to leave France for Switzerland but was denied permission. In March, the Jacobin-dominated Committee of Public Safety came to power, instituting a totalitarian regime meant to mobilise France for the first 'total war'.
Life became very difficult for foreigners in France. At first, they were put under police surveillance and, to get a residency permit, had to produce six written statements from Frenchmen testifying to their loyalty to the republic. Then, on 12 April 1793, all foreigners were forbidden to leave France. Despite her sympathy for the revolution, life for Wollstonecraft become very uncomfortable, all the more so as the Girondins had lost out to the Jacobins. Some of Wollstonecraft's French friends lost their heads to the guillotine as the Jacobins set out to annihilate their enemies.
Wollstonecraft was offended by the Jacobins' treatment of women. They refused to grant women equal rights, denounced 'Amazons', and made it clear that women were supposed to conform to Jean-Jacques Rousseau's ideal of helpers to men. On 16 October 1793, Marie Antoinette was guillotined; among her charges and convictions, she was found guilty of committing incest with her son. Though Wollstonecraft disliked the former queen, she was troubled that the Jacobins would make Marie Antoinette's alleged perverse sexual acts one of the central reasons for the French people to hate her.
As the daily arrests and executions of the Reign of Terror began, Wollstonecraft came under suspicion. She was, after all, a British citizen known to be a friend of leading Girondins. On 31 October 1793, most of the Girondin leaders were guillotined; when Imlay broke the news to Wollstonecraft, she fainted. By this time, Imlay was taking advantage of the British blockade of France, which had caused shortages and worsened ever-growing inflation, by chartering ships to bring food and soap from America and dodge the British Royal Navy, goods that he could sell at a premium to Frenchmen who still had money. Imlay's blockade-running gained the respect and support of some Jacobins, ensuring, as he had hoped, his freedom during the Terror. To protect Wollstonecraft from arrest, Imlay made a false statement to the U.S. embassy in Paris that he had married her, automatically making her an American citizen. Some of her friends were not so lucky; many, like Thomas Paine, were arrested, and some were even guillotined. Her sisters believed she had been imprisoned.