The Abdali historical tradition (recorded in early 19th century) relates that a grand jirga of Abdali clans around Kandahar was held in 1589 AD. To get rid of the feuds between the various clans of Abdali, they decided that the entire tribe should have one malik as had been the case when the tribe dwelt in the Kasi Ghar (Sulaiman mountains range). They selected Malik Saddu because he demonstrated qualities of leadership. Malik Saddu (said to have been born in 1558 A.D) was the ancestor of the ‘Sadduzai tribe’ of Pashtuns, and Ahmad Shah Abdali. ‘Saddu is assumed to be a distortion of either Sardar Khan or Asadullah or Sadullah by some modern historians but he has only been mentioned by name of ‘Saddu’ in the original sources . When Safavids obtained possession of Kandahar, Saddu received the honorific title of “Mir-i-Afghan” and the grant of the Safa town from Shah Abbas the Great of Persia (1571-1629) .
Saddu was succeeded by his eldest son Khwaja Khizr Khan but he had no interest in worldly affairs, therefore, after three months, he abdicated in favour of his younger brother Maudud Khan. The descendants of Khwaja Khizr are called Khizr Khel. Ahmad Shah Abdali was direct descendant of Khwaja Khizr . See the genealogy of Khizr Khel (clan of Ahmad Shah Abdali) here.
Herat becomes new home of the Abdali tribe in early 18th century
In 1707 A.D the Abdalis were expelled from Kandahar by Gurgin Khan (Safavid viceroy of Kandahar). They migrated to Shorawak (see the location on the map here) and subsequently to Bakwa in Farah . In the latter part of 1712 A.D (15th of Ramadan 1124 Hijri) Asadullah Khan, a descendant of Saddu, took Herat during the absence of his father, at Multan. His father Abdullah Khan returned from Multan, enthroned himself as ‘Shah’, took up his residence at Herat and the whole Abdali tribe moved thither. He proclaimed Herat an independent state . Abdalis took possession of Herat, Ghurian, Kuhsan, Bala-Murghab, and Badghis and Obah, and installed their own governors . Abdullah Khan Saddozai and his son, Asadullah, defeated at least four Persian armies sent against them .
In 1718 A.D (1130 Hijri) Abdalis joined with the Uzbeks to attack Persian Khurasan . In 1719 A.D (1131 Hijri) Asadullah Khan Sadduzai, acting as governor of Farah on behalf of his father, moved against Mir Mahmud Hotak (son of Mirwais Hotak) to regain Kandahar but was defeated and slain. Mahmud Hotak sent the head of Asadullah Khan Sadduzai to Sultan Hussain, the Safavid emperor of Persia with a feigned profession of submission and obedience. He then said that he had taken the field against Asadullah out of the loyalty to Persian throne. Impressed, the Safavid Shah heaped honors on Mahmud Hotak . In the meantime, the Jirga of Abdali tribe deemed Asadullah’s father Abdullah unfit to lead them because he was too old and distraught by his son’s death. They elected Zaman Khan (father of Ahmad Shah Abdali) as leader of the Abdalis . Abdullah Khan Sadduzai was thrown into prison, and was there, it is alleged, poisoned or otherwise done to death by Zaman Khan . The murder of Abdullah Khan by Zaman Khan started a cycle of revenge and a series of internal disputes among Abdalis which lasted for several years.
In 1720 Persians made another attempt to retake Herat but were defeated by Abdalis under the leadership of Zaman Khan. Zaman Khan died a natural death after ruling his clan for two years and five months . Among the few attested documentary sources of Zaman Khan’s rule in Herat is a decree he issued in Shaʿban 1131/June-July 1719. The decree declares that Zaman Khan dispatched a certain Yaḥya Khan, the Head of the Diwan (diwan beg), at the head of an Abdali contingent to punish a certain Qasim Baluch who, it is claimed, had been harassing the population and especially the peasantry of the towns of Ṭabas and Qaʾin in southern Khurasan. The decree also requests that the local inhabitants cooperate with the Abdali force. 
When the disaffection had started in Herat, Zaman Khan is said to have sent his wife Zarkuna Alkozai to Multan to his maternal uncle Jalal Khan considering Multan as a safe place. Zaman Khan’s mother was already staying with her brother Jalal Khan in Multan. It is claimed that Zarghuna gave birth to Ahmad Shah Abdali in Jalal Khan’s house in the Kiri Shah Hussain Khan in 1722 (1134 Hijri) . Zarghuna Alakozai is buried in village of Kohak, west of Kandahar.
The elders of Abdali tribe now summoned from his retreat in Shorawak, another son of the late Abdullah Khan, named Muhammad Khan, and made him ruler over themselves . In 1722 Mahmud Hotak conquered Isfahan, encouraged by that Muhammad Khan Abdali attacked Persian Khurasan and besieged Mashhad for four months during the winter of 1722-23, but failed to take it . When the unsuccessful Muhammad Khan Abdali returned to Herat, he was deposed and Zulfiqar Khan (elder brother of Ahmad Shah Abdali) was recalled from Shorawak and made their chief by the Abdalis . In 1725-1726, Rahman, a son of the murdered Abdullah Khan Sadduzai, attacked Zulfiqar Khan to exact revenge. The Abdali elders intervened and decided to expel both factions from Herat city. Zulfiqar Khan was exiled to the district of Bakharz (see the location on map here), and Rahman to Farah. Allahyar Khan, a son of late Abdullah, was invited from Multan and was elected as new chief of the tribe . The peaceful rule of Allahyar Khan Abdali was disturbed by Abdul Ghani Alkozai (maternal uncle of Ahmad Shah Abdali). He instigated and supported Zulfiqar Khan to revolt against Allahyar Khan and the civil war continued for about six months. The Ulus Abdali again expelled both Allahyar and Zulfiqar: the former to Maruchak and the latter this time to Farah .
In November 1726 Nadir Khan Afshar (later Nadir Shah of Persia) captured Mashad. In August 1727 he departed Mashhad to undertake a series of campaigns against Qain, Khwaf and Sangan in Persian Khurasan. In October 1727 he met an Abdali army, 7,000 to 8,000 strong, sent by Allahyar Khan and Zulfiqar Khan to aid the inhabitants of Sangan (see the location on map here). After four days of fighting, however, Abdali army was retreated towards Herat. Nadir Khan, feeling the need of caution because of inexperience of his troops and formidability of Abdalis, refrained from pursuit and returned to Mashhad. 
In the June 1729 (Shawwal 1141 A.H.) Nadir Khan Afshar again took the field against the Abdalis who had been encroaching on the territory they had lost. Nadir Shah could not conquer Herat, but he was satisfied with the nominal submission of Allahyar Khan Abdali. In June 1730 Zulfiqar Khan wrested Herat from Allahyar and advanced towards Mashhad (held by Ibrahim Khan Afshar, brother of Nadir Shah) and besieged it. Ibrahim Khan Afshar led his troops out of the city around the beginning of August to attack the Abdalis, and was soundly beaten. He shut himself in the city till Nadir Shah himself came to the rescue. On hearing the news of Nadir Khan Afshar coming to help his brother, Zulfiqar Khan Abdali went back to Herat. Now it was turn of Nadir Shah Afshar. The latter marched towards Herat in March 1731 (1143 H). On hearing the news, Zulfiqar Khan Abdali request Shah Hussain Hotak of Kandahar for help. The celebrated Ghilzai general Saidal Khan Nasar was dispatched to Herat from Kandahar with a strong army of 3,000 to help Zulfiqar Khan against Nadir Shah. Zulfiqar Khan, even with the help of Saidal Khan, could not repulse the attack of Nadir Shah who was assisted by Allahyar Khan Abdali. One night Saidal Khan Nasar fled to Kandahar which greatly demoralized the defenders. Now Nadir Shah forced Zulfiqar Khan to hand over Herat to Allahyar Khan. Zulfiqar Khan along with his younger brothers Ali Mardan Khan and Ahmad Khan (future Ahmad Shah Durrani) left Herat for Farah. When he reached Farah, he found Saidal Khan there. Saidal Khan took Zulfiqar Khan and his younger brothers to Kandahar with an assurance to get help from Shah Hussain Hotak. But on their arrival at Kandahar, Shah Hussain Hotak treacherously imprisoned them. 
Within a few months Allahyar Khan Abdali renounced his allegiance to Nadir Shah and raised the flag of independence. Herat was again besieged by Nadir Shah. On 27th February 1732, after Nadir promised to spare the lives and not to destroy the city, the fortress gates were opened. Allahyar Khan was exiled with his adherents to Multan. Nadir then transferred some 60,000 members of the Abdali tribe to Mashad, Nishapur, and Damghan of Persian Khurasan . Nadir treated the vanquished Abdalis with marked clemency, since he realized their martial qualities and was determined to win them over by generous treatment to serve in his army .
Afshar : A tribe of Turks dwelling in Khurasan
Hotak : A clan of Ghilzai Afghans
Jirga: A council
Malik : A chief or headman
Nasar: A clan of Ghilzai Afghans
Safavids: They originated from a mystical order appeared among Turkish speaking people of west of the Caspian Sea, at Ardabil, and ruled Persia from 1501 to 1722.
Suleiman mountains: A mountain mass in central Pakistan
Ulus: A clannish commonwealth.
1- “Multans under the Afghans”, by Muhammad Ashiq Durrani, p-11
2- “The Geographical Magazine” , Volume 4 , p-290 (1877)
3- “Multan Under the Afgh̲ans, 1752-1818” , p-12
4- “The Kingdom of Afghanistan ; a historical sketch”, by G.P.Tate, p-42
5- “The Geographical Magazine” , Volume 4 , p-290 (1877)
6- “The Kingdom of Afghanistan: A Historical Sketch”, p-43
7- “Afghanistan” by Louis Dupree, p-324
8- “History of the Mongols From the 9th to the 19th Century”, by Henry Hoyle Howorth, p-762
9- “The Fall of the Safavi Dynasty and the Afghan Occupation of Persia”, L.Lockhart, p-100
10- “The Kingdom of Afghanistan: A Historical Sketch”, G.P.Tate, p-44
11- “Ahmad Shah Durrani: Father of modern Afghanistan” by Ganda Singh, p-10
12- “The Kingdom of Afghanistan: A Historical Sketch”, G.P.Tate, p-44
Shah, Durr-i Durran”, Sajjad Netaji, p-253
13- “The pearl of pearls: The Abdali-Durrani confederacy and its transformation under Ahmad Shah Dur-i-Durran”, by Sajjad Nejatie, p-253
14- “Multans under the Afghans”, by Muhammad Ashiq Durrani, p-20
15- “The Kingdom of Afghanistan: A Historical Sketch”, G.P.Tate, p-44
16- “Multans under the Afghans”, by Muhammad Ashiq Durrani, p-21
17- “Ahmad Shah Durrani: Father of modern Afghanistan” by Ganda Singh, p-10
18- ““The Kingdom of Afghanistan: A Historical Sketch”, G.P.Tate, p-55
19- Ibid, p-55
20- “Nadir Shah”, L.Lockhart, p-29
21- “Multans under the Afghans”, by Muhammad Ashiq Durrani, pp.22-23
23- Hist Afghanistan V 1 & 2, Volume 1 By Percy Sykes, p-333