None of it. Not an inch of Pakistan belongs to Afghanistan historically. The reason being that historical claims are not a real thing. I always find it laughable whenever someone tries to pass off historical claims as something that actually makes sense or matters in the modern world.
Let me provide an example. The Ottoman Empire ruled over much of the Balkans for centuries. It ruled over much of the region of modern-day Greece for about half a millennium. Should Turkey now lay claims over the region of Greece because of some historical claims? Or should Greece lay claims over Turkey based on the control of the Byzantine Empire over Asia Minor? Or perhaps the Italians should claim them both based on the Roman Empire? Or maybe the Persians? We could go on about this forever. This example pretty much shows exactly why historical claims are ridiculous.
Afghanistan can claim much of Pakistan on the basis of the historic Durrani Empire. However, such claims hold no weight in the modern world. Let’s not forget that prior to the rise of the Durrani Empire, Afghanistan itself was a divided land. Eastern Afghanistan was a part of the Mughal Empire, western Afghanistan was a part of the Safavid Empire and northern Afghanistan was under the control of the Uzbek Khanates. This was the status of Afghanistan for centuries. Should we now also divide Afghanistan up on the basis of these historic claims between India, Iran and Uzbekistan as well?
As for the ridiculous myth of the British Empire dividing the Pashtun people. The British never divided the Pashtun people. The Durrani Empire waged a war against the Sikh Empire and lost. That is why Dost Muhammad Khan launched a desperate attempt to take back Peshawar in 1837. However, the Afghans were unable to make any real gains in the Battle of Jamrud. As such, the region remained under the control of the Sikh Empire. The Sikh Empire was defeated and annexed by the British in 1849. That is how the British came in control of the region. Further territory was gained by the British following the signing of the Treaty of Gandamak, after defeating the Afghans in the Second Anglo-Afghan War in 1879. Mortimer Durand came about a decade later. He did not divide the Pashtun people. They had already been divided before the British even came to the region. He just set up spheres of influence and tweaked the border a little bit.
Afghanistan can claim much of Pakistan on the basis of the historic Durrani Empire. However, such claims hold no weight in the modern world. Let’s not forget that prior to the rise of the Durrani Empire, Afghanistan itself was a divided land. Eastern Afghanistan was a part of the Mughal Empire, western Afghanistan was a part of the Safavid Empire and northern Afghanistan was under the control of the Uzbek Khanates. This was the status of Afghanistan for centuries. Should we now also divide Afghanistan up on the basis of these historic claims between India, Iran and Uzbekistan as well?
As for the ridiculous myth of the British Empire dividing the Pashtun people. The British never divided the Pashtun people. The Durrani Empire waged a war against the Sikh Empire and lost. That is why Dost Muhammad Khan launched a desperate attempt to take back Peshawar in 1837. However, the Afghans were unable to make any real gains in the Battle of Jamrud. As such, the region remained under the control of the Sikh Empire. The Sikh Empire was defeated and annexed by the British in 1849. That is how the British came in control of the region. Further territory was gained by the British following the signing of the Treaty of Gandamak, after defeating the Afghans in the Second Anglo-Afghan War in 1879. Mortimer Durand came about a decade later. He did not divide the Pashtun people. They had already been divided before the British even came to the region. He just set up spheres of influence and tweaked the border a little bit.