period) to commit 10,000 soldiers and 2,000 horses to the defense of the other in case of an attack, and secretly agree to maintain security within the Polish–Lithuanian Commonwealth. April 5 – The Sugar Act is passed in Great Britain. April 21 – Residents of French Louisiana are informed for the first time that they will come under Spanish rule as the result of a secret agreement of November 13, 1762 whereby France has ceded all of its North American territory west of the Mississippi River. The Spanish, however, do not take possession until August 17, 1769. April 27 – Eight-year-old child prodigy Wolfgang Amadeus Mozart performs a private concert before King George III and Queen Charlotte in Great Britain, and has an encore on May 19. May 3 – Baden, one of the member states of the Confederation of Switzerland, declares a policy of remaining neutral in future conflicts, a model that is soon followed by other members of the Confederation and which eventually becomes the basis for Swiss neutrality from 1815 onward. June 21 – The English-language Quebec Gazette is established in Quebec City, Canada (the oldest surviving newspaper in North America). June 29 – One of the strongest tornadoes ever recorded hits Woldegk, Germany. July–September July 6 – The last British troops depart Havana, Cuba, two years after having captured it from Spain during the Seven Years' War. The removal of troops follows the treaty between the two Kingdoms, with Spain ceding West Florida to Great Britain in return for the Havana withdrawal. July 8 – The Niagara Conference begins at the invitation of Sir William Johnson, the British Superintendent of Indian Affairs for the northern district, who hosts "one of the largest conventions of red men ever held on the continent" to negotiate the end of the hostilities from the French and Indian War. Reportedly, 2,000 representatives of the North American tribes meet at upstate New York coming from distances ranging "From Dakota to Hudson's Bay, and from Maine to Kentucky." July 11 – Conditional repatriation of the Acadians in Canada, French colonists who took up arms against the British during the war, is approved by order of King George III on advice of the Privy Council. The Council offers settlement to any Acadians willing to take an oath of allegiance to the British Crown and that those living in New Brunswick are to "be allowed