For the time being the 'offensive spirit' was in abeyance; our paramount task was the perfection of our defensive system. By this time in the war it was acknowledged that against attacks in weight no actual line could be held intact. Faith in 'lines' became qualified in favour of the series of 'strong points' or redoubts, which were constructed to defend 'tactical features.' This policy, founded on our experience of the German defence during the Third Battle of Ypres, was very sound. All the redoubts constructed in the area occupied by the 184th Brigade were so well sited and so strongly wired that the faith seemed justified that they were part of one impregnable system. But against loss of one important factor no amount of industry could serve to insure. 'Strong points' must act in concert and for such mutual action 'on the day' good visibility was essential. As we shall see, this factor was denied. In rear of these redoubts, which lay along the ridge west of Fayet, a line known as the 'Battle Line' was fortified, and in rear again a trench was dug to mark the 'Army Line,' where the last stand would be made. These lines were strong, but more reliance was apt to be placed upon their mere existence on the ground than, in default of any co-existent scheme to fill them at a crisis with appropriate garrisons, was altogether justified.[10] [Footnote 10: For the _terrain_ referred to in this chapter see the maps ante pp. 83 and 95.] Early in the year the Bucks had been taken from the Brigade (now like all Infantry Brigades reduced to three Battalions) and went to Nesle to work as an entrenching Battalion. Many old friends, including especially Colonel 'Jock' Muir, had to be parted with. The three Battalions which remained were now arranged in 'depth,' a phrase explained by stating that while one, say the Berks, held the front line 'twixt Fayet and Gricourt, the Gloucesters as Support Battalion would be in Holnon Wood and ourselves, the Oxfords, in reserve and back at Ugny. When a relief took place the Gloucesters went to the front line, ourselves to Holnon, and the Berks back to Ugny. The Battalion holding the line was similarly disposed in 'depth,' for its headquarters and one company were placed more than a mile behind the actual front.