Anglo-American influence effectively ended after 8 December 1941, when the Imperial Japanese Army entered and occupied the British and American controlled parts of the city in the wake of the attack on Pearl Harbor. The British and Americans troops taken by surprise surrendered without a shot, with the exception of the only British riverboat in Shanghai, HMS "Peterel", which refused to surrender: six of the 18 British crew who were on board at the time were killed when the ship was sunk when the Japanese opened fire at almost point-blank range. The French troops did not move from the preserved French Concession, as the French Vichy government considered itself neutral.