Ahmad Shah Durrani (c. 1722 - 16 October 1772) (Pashto: Hmd shh drny), also known as Ahmad Khan Abdali (Hmd khn bdly), was the founder of the Durrani Empire and is regarded as the founder of the modern state of Afghanistan. He began his career by enlisting as a young soldier in the military of the Afsharid kingdom and quickly rose to become a commander of the Abdali Regiment, a cavalry of four thousand Abdali Pashtun soldiers. After the assassination of Nader Shah Afshar in 1747, Ahmad Shah Durrani was chosen as King of Afghanistan.

Nader Shah's rule abruptly ended in June 1747 when he was assassinated by his own guards. The guards involved in the assassination did so secretly so as to prevent the Abdalis from coming to their King's rescue. However, Durrani was told that the Shah had been killed by one of his wives. Despite the danger of being attacked, the Abdali contingent led by Durrani rushed either to save the Shah or to confirm what happened. Upon reaching the Shah's tent, they were only to see his body and severed head. Having served him so loyally, the Abdalis wept at having failed their leader, and headed back to Kandahar. Before the retreat to Kandahar, he had "removed" the royal seal from Nader Shah's finger and the Koh-i-Noor diamond tied "around the arm of his deceased master". On their way back to Kandahar, the Abdalis had "unanimously accepted" Durrani as their new leader. Hence he "assumed the insignia of royalty" as the "sovereign ruler of Afghanistan".  At the time of Nadir's death, he commanded a contingent of Abdali Pashtuns. Realizing that his life was in jeopardy if he stayed among the Persians who had murdered Nader Shah, he decided to leave the Persian camp, and with his 4,000 troops he proceeded to Qandahar. Along the way and by sheer luck, they managed to capture a caravan with booty from India. He and his troops were rich; moreover, they were experienced fighters. In short, they formed a formidable force of young Pashtun soldiers who were loyal to their high-ranking leader.  One of Durrani's first acts as chief was to adopt the titles Padishah-i-Ghazi ("victorious emperor"), and Durr-i-Durrani ("pearl of pearls" or "pearl of the age").

what else interesting happened during his rise to power?
Nader Shah's rule abruptly ended in June 1747 when he was assassinated by his own guards.