Anglo-Afghan Treaty of 1919
The Anglo-Afghan Treaty of 1919, also known as the Treaty of Rawalpindi, was a treaty which brought the Third Anglo-Afghan War to an end. It was signed on 8 August 1919 in Rawalpindi by Great Britain and Afghanistan. Britain recognised Afghanistan's independence, agreed that British India would not extend past the Khyber Pass and stopped British subsidies to Afghanistan. Afghanistan also accepted all previously agreed border arrangements with British India as per Article 5 of the Anglo-Afghan treaty of 1919. Thus, Afghanistan as an independent country agreed to recognise Durand Line as international border between the two countries.
This treaty could be cancelled by both parties within three years of signing but neither party cancelled it. So this became an internationally recognised border agreement.