attacks have been criticised as amateurish, poorly co-ordinated, in insufficient strength and with inadequate artillery support but most German counter-attacks were similarly poorly organised and defeated in detail. After the first few days, battalions had been withdrawn from German divisions to the south and sent to the Somme and on the south bank, XVII Corps () had battalions from eleven divisions under command. Despite their difficulties, the British captured elaborately fortified and tenaciously defended German positions relatively quickly, by local initiatives from regimental officers. By 13 July the British–French had captured and The crisis in the French defence of Verdun had been overcome, with a relaxation of German pressure on 24 June and a "strict defensive" imposed by Falkenhayn on 12 July after the failure at Fort Souville. The battles at Verdun and the Somme had reciprocal effects and for the rest of 1916, both sides tried to keep their opponent pinned down at Verdun to obstruct their efforts on the Somme. Harris, 2009 Also in 2009, J. P. Harris wrote that the difference between the Franco-British success in the south and British failure in the north on 1 July, particularly given the number of British casualties on the first day, had been explained by reference to greater French experience, better artillery and superior infantry tactics. On the first day, the French artillery had been so effective that infantry tactics were irrelevant in places; on the south bank, the French attack took the defenders by surprise. Harris noted that the British had also succeeded in the south and the victory was in the area expected to be least successful. Harris wrote that it was common to ignore the influence of the opponent and that the Germans were weakest in the south, with fewer men, guns and fortifications, based on terrain less easy to defend and had made their principal defensive effort north of the Somme, where the British–French had also made their main effort. Low ground on the south bank left the Germans at a tactical disadvantage against British–French air power, which kept the skies clear of German aircraft, as artillery-observation and contact-patrol aircraft spotted for French artillery and kept headquarters relatively well informed. Harris wrote that the objective in the south was the German first position, which had been demolished by the French artillery. Harris blamed Haig for the decision to attempt to take the second German position north