Passage: During World War II, San Marino remained neutral, although it was wrongly reported in an article from The New York Times that it had declared war on the United Kingdom on 17 September 1940.  The Sammarinese government later transmitted a message to the British government stating that they had not declared war on the United Kingdom.Three days after the fall of Benito Mussolini in Italy, PFS rule collapsed and the new government declared neutrality in the conflict. The Fascists regained power on 1 April 1944 but kept neutrality intact. Despite that, on 26 June 1944, San Marino was bombed by the Royal Air Force, in the belief that San Marino had been overrun by German forces and was being used to amass stores and ammunition. The Sammarinese government declared on the same day that no military installations or equipment were located on its territory, and that no belligerent forces had been allowed to enter. San Marino accepted thousands of civilian refugees when Allied forces went over the Gothic Line. In September 1944, it was briefly occupied by German forces, who were defeated by Allied forces in the Battle of San Marino.

Question: When did the allies defeat the German forces at the Battle of San Marino?
September 1944