In December 1939 the 159th Brigade was sent to Northern Ireland to join the 158th and 160th Infantry brigades which had been sent earlier in the year. When the British Expeditionary Force (BEF) fighting in France and Belgium was evacuated from the continent in the Dunkirk evacuation the brigade began training to repel an invasion (Operation Green, which never took place). The brigade was to remain there until March 1942 when it was sent, with the rest of the 53rd Division, to Kent.