▁Y pres ▁The ▁Germ ans ▁launched ▁an ▁attack ▁preced ed ▁by ▁poison ▁gas ▁at ▁Y pres ▁on ▁ 2 2 ▁April . ▁On ▁ 2 3 ▁and ▁ 2 4 ▁April ▁the ▁ 1 / 4 th ▁B n ▁force - m arch ed ▁towards ▁the ▁Y pres ▁Sal ient ▁and ▁went ▁into ▁the ▁firing ▁line ▁on ▁ 2 6 ▁April , ▁dig ging ▁new ▁assembly ▁tren ches ▁on ▁a ▁reverse ▁slope . ▁At ▁ 1 4 . 3 0 ▁the ▁batt alion ▁moved ▁up ▁in ▁support ▁of ▁a ▁British ▁counter - att ack , ▁but ▁the ▁attack ▁had ▁failed , ▁and ▁the ▁Lond ons ▁march ed ▁across ▁open ▁ground ▁under ▁sh rap nel ▁shell ▁fire ▁to ▁a ▁sun ken ▁l ane ▁where ▁the ▁rem n ants ▁of ▁the ▁attack ers ▁were ▁shelter ing . ▁Here ▁they ▁d ug ▁a ▁new ▁temporary ▁line . ▁The ▁following ▁day ▁the ▁attack ▁was ▁renew ed , ▁the ▁batt alion ▁coming ▁under ▁fire ▁as ▁it ▁crossed ▁the ▁cr est ▁line . ▁He avy ▁cas ual ties ▁were ▁suffered ▁in ▁the ▁valley ▁beyond , ▁until ▁the ▁batt alion ▁was ▁with dra wn ▁into ▁brig ade ▁reserve ▁after ▁night fall . ▁The ▁F ero ze p ore ▁Brigade ▁was ▁rel ieved ▁on ▁ 3 0 ▁April ▁and ▁with d rew ▁under ▁shell fire . ▁Between ▁ 2 6 ▁and ▁ 3 0 ▁April ▁the ▁ 1 / 4 th ▁Lond ons ▁had ▁lost ▁ 3 6 5 ▁out ▁of ▁ 6 0 0 ▁men ; ▁while ▁withdraw ing ▁it