 Complete the following phrase:  The line held by the division was on the La Bassée front from Mad Point to Givenchy, just north of the Hohenzollern Redoubt, scene of bitter fighting the previous autumn, but now considered a quiet sector suitable for newly-arrived formations. But there was active Tunnel warfare in this sector, leading to further actions at the Hohenzollern Redoubt. The divisional artillery had to be prepared to put down an SOS barrage at any time when a mine was exploded followed by an infantry raid. On 27 April a German mine was fired and 33rd Division was attacked with heavy gas shelling. Following this attack the batteries were subjected to several days of CB fire. On 22 June a German mine near Givenchy required every available gun to fire SOS missions. On 27 June a British trench raid at Mad Point was covered by a Box barrage fired by the divisional artillery. Further raids were carried out on 2 and 5 July as diversions from the 