Operation Tractable was the final attack conducted by Canadian and Polish troops, supported by a British tank brigade, during the Battle of Normandy during World War II. The operation was to capture the tactically important French town of Falaise and then the smaller towns of Trun and Chambois. This operation was undertaken by the First Canadian Army with the 1st Polish Armoured Division and a British armoured brigade against Army Group B of the Westheer in what became the largest encirclement on the Western Front during the Second World War. Despite a slow start and limited gains north of Falaise, novel tactics by the 1st Polish Armoured Division during the drive for Chambois enabled the Falaise Gap to be partially closed by 19 August 1944, trapping about 150,000 German soldiers in the Falaise Pocket.