 In the centre of the attack , a company from each battalion advanced behind the barrage , to an observation line several hundred yards down the east slope of the ridge , at 8 : 40 a.m. assisted by eight tanks and patrols of cavalry . Most German troops encountered surrendered quickly , except at Leg Copse and Oosttaverne Wood where they offered slight resistance . British aircraft added to German difficulties , with low @-@ level machine @-@ gun attacks . The second objective ( the observation line ) from <unk> Farm to south of Messines , <unk> Farm and Oosttaverne Wood , was reached with few casualties . Ground markers were put out for the three divisions due to attack in the afternoon and the area consolidated . The defensive frontages of the British units on the ridge had been based on an assumption that casualties in the advance to the first intermediate objective ( blue line ) would be 50 percent and in the advance to the ridge ( black line ) would be 60 percent . There were far fewer British casualties than anticipated , which caused congestion on the ridge , where the attacking troops suffered considerable casualties from German long @-@ range machine @-@ gun and artillery fire . The British planners expected that the two German Eingreif divisions behind the ridge , would begin organised counter @-@ attacks at about 11 : 00 a.m. and arranged for a long pause in the advance down the eastern slope , to enable them to be defeated from consolidated defensive positions , rather than encountered in the open while the British were still advancing . The masked batteries of the three reserve divisions were used to add to the protective barrage in front of the infantry but no Germans could be seen . 
