Afghanistan is an Islamic republic where Islam is practiced by 99.7% of its population. Roughly 90% of the Afghans follow Sunni Islam. The remaining are Shias. Apart from Muslims, there are also small minorities of Sikhs and Hindus.
The religion Zoroastrianism is believed by some to have originated in what is now Afghanistan between 1800 and 800 BC, as its founder Zoroaster is thought to have lived and died in Balkh while the region at the time was referred to as Ariana. Ancient Eastern Iranian languages may have been spoken in the region around the time of the rise of Zoroastrianism. By the middle of the 6th century BC, the Achaemenids overthrew the Medes and incorporated Arachosia, Aria, and Bactria within its eastern boundaries. An inscription on the tombstone of Darius I of Persia mentions the Kabul Valley in a list of the 29 countries that he had conquered.
Following Alexander the Great's conquest and occupation in the 4th century BC, the successor-state Seleucid Empire controlled the area until 305 BC when they gave much of it to the Indian Maurya Empire as part of an alliance treaty. The Mauryans brought Buddhism from India and controlled southern Afghanistan until about 185 BC when they were overthrown.
In the 7th century, the Umayyad Arab Muslims entered into the area now known as Afghanistan after decisively defeating the Sassanians in the Battle of Nihawand (642 AD). Following this colossal defeat, the last Sassanid Emperor, Yazdegerd III, became a hunted fugitive and fled eastward deep into Central Asia. In pursuing Yazdegerd, the Arabs chose to enter the area from north-eastern Iran and thereafter into Herat, where they stationed a large portion of their army before advancing toward the rest of Afghanistan. The Arabs exerted considerable efforts toward propagating Islam amongst the locals.
A large number of the inhabitants of the region of northern Afghanistan accepted Islam through Umayyad missionary efforts, particularly under the reigns of Hisham ibn Abd al-Malik (caliph from 723 to 733) and Umar ibn AbdulAziz (caliph from 717 to 720). During the reign of Al-Mu'tasim Islam was generally practiced amongst most inhabitants of the region and finally under Ya'qub-i Laith Saffari, Islam was by far, the predominant religion of Kabul along with other major cities of Afghanistan. Later, the Samanids propagated Islam deep into the heart of Central Asia, as the first complete translation of the Qur'an into Persian occurred in the 9th century. Since the 9th century, Islam has dominated the country's religious landscape. Islamic leaders have entered the political sphere at various times of crisis, but rarely exercised secular authority for long. The remnants of a Shahi presence in Afghanistan's eastern borders were expelled by Mahmud of Ghazni during 998 and 1030.
Until the 1890s, the country's Nuristan region was known as Kafiristan (land of the kafirs or "infidels") because of its inhabitants: the Nuristani, an ethnically distinctive people who practiced animism, polytheism and shamanism.
The 1979 Soviet invasion in support of a communist government triggered a major intervention of religion into Afghan political conflict, and Islam united the multi-ethnic political opposition. Once the Soviet-backed Marxist-style regime came to power in Afghanistan, the People's Democratic Party of Afghanistan (PDPA) moved to reduce the influence of Islam. The "atheistic" and "infidel" communist PDPA imprisoned, tortured and murdered many members of the religious establishment. After National Reconciliation talks in 1987, Islam became once again the state religion and the country removed the word "Democratic" from its official name. From 1987-1992, the country's official name was the Republic of Afghanistan but today it is an Islamic Republic. For Afghans, Islam represents a potentially unifying symbolic system which offsets the divisiveness that frequently rises from the existence of a deep pride in tribal loyalties and an abounding sense of personal and family honor found in multitribal and multiethnic societies such as Afghanistan. Mosques serve not only as places of worship, but for a multitude of functions, including shelter for guests, places to meet and converse, the focus of social religious festivities and schools. Almost every Afghan has at one time during his youth studied at a mosque school; for some this is the only formal education they receive.
The Shias make up roughly 10% of the total population of Afghanistan. Although there are some Sunnis among them, the Hazaras practice Shia Islam, mostly of the Twelver branch with some smaller groups who practice the Ismailism branch. The Qizilbash Tajiks of Afghanistan have traditionally been Shias.
According to the Christian Encyclopedia, 2,000 Afghans identified as Zoroastrians in 1970.
The Bahá'i Faith was introduced to Afghanistan in 1919 and Bahá'í have been living there since the 1880s. Currently, there are approximately 400 Bahá'í (according to a recent estimate) in Afghanistan.
Some unconfirmed reports state that there are 500 to 8,000 Afghan Christians practicing their faith secretly in the country. A 2015 study estimates some 3,300 believers in Christ from a Muslim background residing in the country. Many native Armenian Christian Afghans left the country due to economic reasons.
There was a small Jewish community in Afghanistan who fled the country before and after the 1979 Soviet invasion, and one individual, Zablon Simintov, still remains today. It is thought that there are between [] secret Jews in Afghanistan who were forced to convert to Islam after the Taliban took control of the country. There are Afghan Jewish communities in Israel, the United States, Canada and the United Kingdom.
January Violence Is the Last Straw-After 10 Years of War, Virtually All 50,000 Hindus have Fled, Forsaking