The 'Durand Line' is the international boundary between:

The Durand Line is the roughly 2,640 km long boundary between Pakistan and Afghanistan.

History:

• It was established in 1893 through an agreement between Sir Mortimer Durand, the Foreign Secretary of British India, and Abdur Rahman Khan, the Amir of Afghanistan.
• The line marked the limits of British influence and divided Pashtun and Baloch tribal areas between British India and Afghanistan.
• After the partition of 1947, Pakistan inherited the line as its border with Afghanistan.

Dispute over the line:

• Afghanistan has never formally accepted the Durand Line as an international border.
• Afghan governments, including the Taliban government, argue that it was imposed by the British and divides the Pashtun people.
• Pakistan regards it as a legal international border and has fenced much of it.
• The line passes through difficult mountain terrain, including the Hindu Kush and Spin Ghar ranges, and important passes such as the Khyber Pass and the Bolan Pass.

Ethnic and political issues:

• Millions of Pashtuns live on both sides of the line, in Pakistan's Khyber Pakhtunkhwa province and in eastern and southern Afghanistan.
• The border region has seen insurgency, cross-border movement and clashes between the two countries.

Other famous boundary lines:

• McMahon Line: between India and China (Tibet) in the eastern sector, drawn in 1914 at the Simla Convention; China does not accept it.
• Hindenburg Line: a German defensive line in the First World War, between Germany and France.
• Maginot Line: a French defensive line along the border with Germany before the Second World War.
• Oder-Neisse Line: the border between Germany and Poland.
• 49th Parallel: the boundary between the USA and Canada.

Why not the other options?

• ✗The India-China and India-Pakistan boundaries are different lines, covered in separate questions.
• ✗Afghanistan and Iran share a separate border.