[3][4] Territorial disputes along the widely known "Durand Line" and conflicting claims prevented the normalization of bilateral ties between the countries throughout the mid-20th century.

[13] The Taliban-led Afghan government has also accused Pakistan of undermining relations between Afghanistan and China and creating discord between the neighbouring countries.

[21] Southern and eastern Afghanistan is predominately Pashto-speaking, like the adjacent Khyber-Pakhtunkhwa, Federally Administered Tribal Areas, and northern Balochistan regions in Pakistan.

The single-page agreement, which contained seven short articles, was signed by Durand and Khan, agreeing not to exercise political interference beyond the frontier line between Afghanistan and what was then the British Indian Empire.

Concurrently, the Afridi tribesmen began to rise up in arms against the British, creating a zone of instability between Peshawar and the Durand Line.

As a result, travel across the boundary was almost entirely halted, and the Pashtun tribes living under the British rule began to orient themselves eastward in the direction of the Indian railways.

Shortly after Pakistani independence, Afghanistan materially supported the failed armed secessionist movement headed by Mirzali Khan against Pakistan.

They also tore down the Pakistani flag, to protest against the unification of the Pashtun-dominated North-West Frontier Province into West Pakistan as part of the One Unit policy.

In January 1950, the Afghan king, Mohammed Zahir Shah, had an anti-Pakistan speech which was condemned by Pakistan's Liaquat Ali Khan.

[36] A serious incident took place on September 30, 1950, when Pakistan claimed Afghan troops had crossed into their territory near the Bogra Pass as a low-scale invasion.

[42] Afghanistan's policies placed a severe strain upon Pakistan–Afghan relations in the 1960s, up until the 1970s, when the Pashtunistan movement largely subsided as the population came to identify with Pakistan.

Despite the weaknesses of the early secessionist movement, this period in history continues to negatively influence Pakistan-Afghanistan relations in the 21st century, in addition to the province's politics.

[43] In order to solve the disputes, mainly centered around the borders issue with the Durand line, Khurshid Mahmud Kasuri, a veteran diplomat who served as the Minister of Foreign Affairs of Pakistan (2002–2007), says that "at one time serious efforts were made at government level for an Afg–Pak Confederation", precising that these initiatives were taken during the time of President Mohammed Daoud Khan, generally considered to be anti-Pakistan for his galvanization of the Pashtunistan issue.

Aslam Khattak, a politician who also served as an ambassador to Afghanistan, talked about this process in his book A Pathan Odyssey, and says that Prime Minister Malik Firoz Khan Noon and President Iskandar Mirza both agreed with the plans, the former also agreeing to take King Zahir Shah "as the constitutional Head of State", proclaiming that "after all, for some time after independence, we had a Christian Queen (Elizabeth II).

"Charles Wilson recalled a map that Zia had also shown to him in which overlay indicated the goal of a confederation embracing first Pakistan and Afghanistan and eventually Central Asia and Kashmir.

"[49] Even more than a confederation, recently declassified CIA documents point out that, in 1954, the Afghan government approached the US in order to have a merger with Pakistan, being threatened by the Soviet Union's economic envelopment.

For instance, scholar Muhammad Shamsuddin Siddiqi says that "Ahmed Shah's empire with its power base in Kandahar, and later transferred to Kabul, incorporated Kashmir, Punjab, Sind and Baluchistan" and thus "the Durrani empire bears the closest resemblance to Pakistan",[51] while others have noted that "since the Durrani Empire included the present-day Pakistan and Afghanistan, the forces of history, the principle of national self-determination, and the aspiration for the unity of Muslim Ummah have all come into line",[52] explaining the interconnected geopolitics of both countries, its latest example being the AfPak doctrine, theorized under the Obama administration from 2008 onward, concluding that Afghanistan and Pakistan should be the aim of common security policies considering their similarities.

[54] The figures included Gulbuddin Hekmatyar and Ahmad Shah Massoud-both members of the Jamiat-e Islami students' political society-[55] and the Haqqanis.

This was followed by the execution of deposed Pakistani Prime Minister Zulfikar Ali Bhutto in April 1979 and the assassination of Afghan leader Nur Muhammad Taraki in September 1979.

In turn, Afghan, Indian and Soviet intelligence agencies played their role by supporting al-Zulfikar – a Pakistani leftist terrorist group responsible for the March 1981 hijacking of a Pakistan International Airlines (PIA) plane.

[58] The Bhutto family and Pakistani military dictator Zia-ul-Haq shared a common enemy, as Zia was the one supporting attacks against the Afghan government.

[60][clarification needed] During the 1980s, the Durand Line was heavily used by Afghan refugees fleeing the Soviet occupation in Afghanistan, including a large number of Mujahideen insurgent groups who crossed back and forth.

[62] Following the death of Pakistani President Zia-ul-Haq in 1988, U.S. State Department blamed the WAD (a KGB created Afghan secret intelligence agency) for terrorist attacks inside Pakistan in 1987 and 1988.

[68][69] Although the victorious mujahideen formed a government in 1992 through the Peshawar Accords, Pakistan remained unhappy with new leaders Rabbani and Massoud, including their foreign policy of maintaining friendly relations with India as during the communist era.

Omar called Babar, who was an ethnic Pashtun, a traitor for saying that "all problems would be resolved" should the Durrand Line be recognised by the Taliban government.

When the Islamic Emirate of Afghanistan was toppled and the new Afghan government was formed, President Hamid Karzai began repeating the previous Taliban statement.

[76] Relations have become more strained after the Afghan government began openly accusing Pakistan of using its ISI spy network in aiding the Taliban and other militants.

[111] In July 2010, a Memorandum of understanding (MoU) was reached between Pakistan and Afghanistan for the Afghan-Pak Transit Trade Agreement (APTTA), which was observed by U.S. Secretary of State Hillary Clinton.

The ceremony was attended by Richard Holbrooke, U.S. Special Representative for Afghanistan and Pakistan, and a number of foreign ambassadors, Afghan parliamentarians and senior officials.

[34] The APTTA allows Afghan trucks to drive inside Pakistan to the Wagah border with India, and also to the port cities of Karachi and Gwadar.