Short answers, pulled from the story.
The Safavid dynasty was founded about 1501 when Shah Ismail I captured Tabriz and proclaimed himself King of Kings. The dynasty ruled until 1722 when Isfahan fell to the Afghans, with a brief restoration from 1729 to 1736, after which Nader Shah crowned himself shah and formally ended Safavid rule. A puppet Safavid regime briefly continued until 1760.
Shah Ismail I established Twelver Shi'ism as the official state religion of Safavid Iran after capturing Tabriz in July 1501. This declaration is considered one of the most important turning points in the history of Islam, as it created a lasting confessional divide with the neighboring Sunni Ottoman Empire.
The Qizilbash were Turkoman tribes whose name, a Turkic word meaning "red-head," referred to their distinctive red headgear. They were the primary military and political force that brought the Safavids to power. Their tribal rivalries created chronic instability, prompting later shahs to build a rival military force of Caucasian slave soldiers known as gholams.
At the Battle of Chaldiran in 1514, the Ottoman army, at least double the size of Ismail I's forces and equipped with artillery the Safavids lacked, defeated and briefly occupied Tabriz. The defeat destroyed Ismail's belief in his own divine invincibility and triggered a decade of civil war among the Qizilbash after his death in 1524. It also opened more than 300 years of recurring Ottoman-Safavid warfare.
Shah Abbas I replaced the Qizilbash tribal forces with a standing army of Caucasian slave soldiers, building a cavalry of 10,000-15,000 ghulam regiments armed with muskets, a corps of 12,000 musketeers and artillerymen, and a personal bodyguard of 3,000 Caucasians, totaling near 40,000 soldiers loyal directly to the shah. He could also field 500 cannons in a single battle. English brothers Anthony and Robert Shirley, who arrived in 1598, helped reorganize the army.
Shah Soltan Hoseyn's disinterest in governance left Iran's frontiers repeatedly raided throughout the late seventeenth and early eighteenth centuries. When he attempted to forcibly convert his Afghan subjects in Qandahar from Sunni Islam to Twelver Shi'ism, a Ghilzai Afghan chieftain named Mirwais Hotak revolted. In 1722, Mirwais's son Mahmud defeated the Safavid forces at the Battle of Gulnabad and besieged Isfahan until Soltan Hoseyn abdicated.