▁ground ed ▁Royal ▁F lying ▁Corps ▁( R FC ) ▁reconna issance ▁aircraft ▁and ▁made ▁art illery ▁observation ▁impossible . ▁The ▁L ys ▁was ▁ ▁wide ▁and ▁ ▁deep ▁and ▁fl ank ed ▁by ▁water ▁me adows . ▁The ▁banks ▁were ▁cut ▁by ▁bog gy ▁streams ▁and ▁dy kes , ▁which ▁kept ▁the ▁caval ry ▁on ▁the ▁roads ; ▁German ▁out posts ▁were ▁pushed ▁back ▁but ▁dis mount ed ▁caval ry ▁attacks ▁could ▁not ▁dis l odge ▁the ▁German ▁def enders ▁and ▁the ▁caval ry ▁in ▁War net on ▁town ▁were ▁with dra wn ▁during ▁the ▁night . ▁The ▁attack ▁was ▁res umed ▁on ▁ 1 8 ▁October , ▁when ▁the ▁caval ry ▁attacked ▁from ▁De û l ém ont ▁to ▁Ten b ri elen ▁but ▁made ▁no ▁progress ▁against ▁a ▁strong ▁and ▁well - organ ised ▁German ▁defence , ▁ending ▁the ▁day ▁opposite ▁De û l ém ont ▁in ▁the ▁south ▁to ▁the ▁railway ▁at ▁Ten b ri elen ▁to ▁the ▁north . ▁From ▁ ▁the ▁Caval ry ▁Corps ▁had ▁ ▁The ▁encounter ▁battle ▁ended ▁and ▁subsequent ▁operations ▁in ▁the ▁Battle ▁of ▁Mess ines ▁took ▁place ▁after ▁the ▁end ▁of ▁the ▁" R ace ▁to ▁the ▁Sea ". ▁ ▁Battle ▁of ▁Ar ment ières , ▁ 1 3 ▁October ▁– ▁ 2 ▁November ▁ ▁On ▁ 1 1 ▁October , ▁the ▁British ▁III ▁Corps ▁compr ising ▁the ▁ 4 th ▁and ▁ 6 th ▁divisions , ▁arrived ▁by ▁rail ▁at ▁St . ▁O mer ▁and ▁Haz eb rou ck ▁and ▁then ▁advanced