Napoleon Bonaparte forms an advanced guard (3,500 infantry and 1,500 cavalry) under General Claude Dallemagne. He sends this force along the south bank of the Po River, to cross it with boats at Piacenza. May 10 War of the First Coalition – Battle of Lodi: General Napoleon Bonaparte defeats the Austrian rearguard, in forcing a crossing of the bridge over the Adda River in Italy. The Austrians lose some 2,000 men, 14 guns, and 30 ammunition wagons. Persian Expedition of 1796: Russian troops storm Derbent. May 14 – Edward Jenner administers the first smallpox vaccination, in England. May 15 – Napoleon's troops take Milan. May 20 – The last mock Garrat Elections are held in Surrey, England. June 1 The French-Republican army divisions of the Army of Italy invade the territories of Venice. Tennessee is admitted as the 16th U.S. state. June 6–7 – Ragunda lake in Sweden bursts and drains completely leaving the Döda fallet dry. June 21 – British explorer Mungo Park becomes the first European to reach the Niger River. June 23 – Napoleon Bonaparte seizes the Papal States, which become part of the revolutionary Cisalpine Republic. Pope Pius VI signs the Armistice of Bologna, and is forced to pay a contribution (34 million francs). July–September July 10 – Carl Friedrich Gauss discovers that every positive integer is representable as a sum of at most 3 triangular numbers. July 11 – The United States takes possession of Detroit from Great Britain, under the terms of the Jay Treaty. July 21 – Mungo Park reaches Ségou, the capital of the Bamana Empire. July 22 – Surveyors of the Connecticut Land Company name an area in Ohio Cleveland, after Gen. Moses Cleaveland, the superintendent of the surveying party. July 29 – The Habsburg army under Marshal Wurmser advances from the Alps, and captures Rivoli and Verona. The French abandon the east bank of the Mincio River, the outnumbered division (15,000 men) of Masséna retreats towards Lake Garda. August 4 – French Revolutionary Wars: Battle of Lonato – The French Army of Italy under Napoleon crushes an Austrian brigade. August 5 – French Revolutionary Wars: Battle of Castiglione – The French Army of Italy under Napoleon defeats the Habsburg army (25,000 men) under Marshal Wurmser, who thus fails to break the Siege of Mantua (1796–97), and is forced to retreat north up the Adige Valley. August 9 – The Wearmouth