With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: The Verdun lesson learnt, the Allies' tactical aim became the achievement of air superiority and until September, German aircraft were swept from the skies over the Somme. The success of the Allied air offensive caused a reorganisation of the German air arm and both sides began using large formations of aircraft rather than relying on individual combat. After regrouping, the battle continued throughout July and August, with some success for the British despite the reinforcement of the German lines. By August, General Haig had concluded that a breakthrough was unlikely and instead, switched tactics to a series of small unit actions. The effect was to straighten out the front line, which was thought necessary in preparation for a massive artillery bombardment with a major push.
text_B: Were General Haig's superiors likely disappointed by his reports to them in August?
YES.