three waves. A second battalion followed each of the leading battalions in the same formation, ready to leapfrog beyond and a second brigade followed the first as a reserve. Six lines of infantry, with the soldiers apart had confronted the German defence. Lines and waves had been made thinner and shallower after 1915. On 14 July 1916, in the attack on Longueval, the 9th (Scottish) Division advanced with four battalions. Companies were arranged in columns of platoons, creating four platoon waves apart. One of the attacking brigades advanced with each battalion on a two-company front with two companies behind and a second battalion following on. Each section of the front was attacked by sixteen platoon waves. Six platoons had attacked on a front of about , roughly one soldier every . German On the Somme front, the construction plan ordered by Falkenhayn in January 1915 had been completed. Barbed wire obstacles had been enlarged from one belt wide to two belts wide and about apart. Double and triple thickness wire was used and laid high. The front line had been increased from one trench to three, dug apart, to create a front position, the first trench () occupied by sentry groups, the second () for the front-trench garrison and the third trench for local reserves. The trenches were traversed and had sentry-posts in concrete recesses built into the parapet. Dugouts had been deepened from to , apart and large enough for An intermediate line of strongpoints () about behind the front position, wired for all-round defence, had also been built. Communication trenches ran back to the reserve lines, renamed the second position, which was as well built and wired as the first position. The second position was beyond the range of Allied field artillery, to force an attacker to stop an advance for long enough to move artillery forward. Prelude Anglo-French offensive preparations Aircraft For long-distance reconnaissance, bombing and attacks on (the Imperial German Flying Corps up to October, then , [German Air Force]), the 9th (Headquarters) Wing of the Royal Flying Corps (RFC) was moved to the Somme front, with 21, 27, 60 squadrons and part of 70 Squadron. The Fourth Army had the support of IV Brigade RFC, with two squadrons of the 14th (Army) Wing, four squadrons of the 3rd Wing and 1 Kite Balloon Squadron, with a section for each corps. Corps squadrons, 3, 4, 9