The British telephone system proved vulnerable to German artillery-fire and the movement of troops along communication trenches was delayed by far more than the most pessimistic expectations. Equilibrium between attack and defence quickly resumed, which could only be upset by another set-piece attack, after a delay for preparation which gave the defenders just as much time to reorganise. The attack front was found to have been wide enough to overcome the small number of German reserves but the attackers had not been ordered to assist units which had been held up. British reinforcements were sent to renew failed attacks rather than reinforce success. Small numbers of German troops in strong-points and isolated trenches, had been able to maintain a volume of small-arms fire sufficient to stop the advance of far greater numbers of attackers.