The small British Expeditionary Force, moving up into Belgium on the left flank of the French 5th Army, met with the full weight of the German 1st Army advancing towards Paris under the Schlieffen Plan. A short but intense fire fight - where the British caused heavy casualties to the thick masses of enemy infantry - was followed by a British withdrawal out of the canal salient. This manoeuvre was made more urgent by news that the French Army on the right flank was in retreat.