With the rest of the division, the 143rd Brigade fought in the battles of Belgium and France in May–June 1940 against the German Army but was forced to retreat to Dunkirk, where the 143rd Brigade in particular fought in the battle of the Ypres-Comines Canal. With the rest of the BEF, most of the brigade and division were evacuated to England after the Germans threatened to cut off the BEF from the main French Armies which would likely have caused the annihilation of the BEF.