 Meticulously planned and well executed , the assault secured its objectives in fewer than twelve hours . The combination of tactics devised on the Somme and at Arras , the use of mines , artillery survey , creeping barrages , tanks , aircraft and small @-@ unit fire @-@ and @-@ movement tactics , created a measure of surprise and allowed the attacking infantry to advance by infiltration when confronted by intact defences . Well @-@ organised mopping @-@ up parties prevented by @-@ passed German troops from firing on advanced troops from behind . The British took 7 @,@ 354 prisoners , 48 guns , 218 machine @-@ guns and 60 trench mortars . The offensive secured the southern end of the Ypres salient in preparation for the British " Northern Operation " . Laffert , commander of Gruppe Wijtschate , was sacked two days after the battle . 
