 On 14 August , Canadian forces launched Operation Tractable , in conjunction with American movements northwards to Chambois . On 19 August , a brigade of the Polish 1st Armoured Division linked up with forces of the 90th U.S. Infantry Division , sealing off some 50 @,@ 000 German troops in the pocket . By 21 August , German attempts to reopen the gap had been thwarted , and all German troops trapped in the pocket surrendered to Allied forces , effectively putting an end to the German 7th Army . 
