Passage: On 8 October, the First and Third British Armies broke through the Hindenburg Line at the Second Battle of Cambrai. This collapse forced the German High Command to accept that the war had to be ended. The evidence of failing German morale also convinced many Allied commanders and political leaders that the war could be ended in 1918; previously, all efforts had been concentrated on building up forces to mount a decisive attack in 1919.

Question: after the war had ended, the collapse forced who to accept it?
German High Command