The Allies' Operation "Tractable" in mid-August aimed to control the Falaise area and prevent the enemy from passing through. Located between Argentan and Falaise, Trun was an important element of the plan to close the Falaise "gap" and trap the Germans in the region. "Tractable" called for the 2nd Canadian Infantry Division to take Falaise, which would leave the only main escape route between Argentan and Trun. The 4th Armoured Division -- in particular, The Canadian Grenadier Guards and The Lake Superior Regiment -- and the Polish Armoured Division would then advance on Trun, with the Polish troops continuing on to Chambois. The Americans, meanwhile, would push from Argentan to Chambois.
By the 18th of August, the German attempts to escape the region were reaching a peak. The Canadian Grenadier Guards waited for The Lake Superior Regiment to meet them for their attack on Trun that day. The Germans evidently were not trying to hold the town, and it was easily occupied by the 10th Infantry Brigade. For their part, the Polish division arrived east of the town and prepared to advance to Chambois. Meanwhile, elements of The South Alberta Regiment and The Argyll and Sutherland Highlanders of Canada passed through Trun to drive to St-Lambert-sur-Dives and later Chambois. The gap was almost closed. Trun was in Allied hands, but the Germans were nearby, pouring through the slender and narrowing escape route. Allied airmen inflicted major damage on enemy troops and equipment, and in many instances on Polish and Canadian troops.
At Trun the next day, The Lincoln and Welland Regiment and the 10th Independent Machine Gun Company (the New Brunswick Rangers) managed to prevent German troops from breaking out to cross the river Dives.
On the night of the 19th, contact between Allied forces was at last made, with the Americans and Poles linking at Chambois. Except for a narrow gap between
Chambois and St-Lambert, the enemy was encircled, albeit loosely. Finally, in the afternoon of August 21, the gap was fully closed. By then the Polish troops,
who had been cut off from the Allies by the fleeing Germans, were in desperate need of resupply.