During the 2nd century BCE, the Maurya Empire became a collage of regional powers with overlapping boundaries. The whole northwest attracted a series of invaders between 200 BCE and 300 CE. The Puranas speak of many of these tribes as foreigners and impure barbarians (Mlecchas). First the Satavahana dynasty and then the Gupta Empire, both successor states to the Maurya Empire, attempt to contain the expansions of the successive before eventually crumbling internally due pressure exerted by these wars.
The invading tribes were influenced by Indian religions such as Buddhism and Hinduism which continued to flourish under the patronage of both invaders and the Satavahanas and Guptas and provides a cultural bridge between the two cultures. Over time, the invaders became "Indianized" as they influenced society and philosophy across the Gangetic plains and were conversely influenced by it. This period is marked by both intellectual and artistic achievements inspired by cultural diffusion and syncretism as the new kingdoms straddle the Silk Road.
The Indo-Scythian Sakas
The Indo-Scythians are a branch of the Sakas who migrated from southern Siberia into Bactria, Sogdia, Arachosia, Gandhara, Kashmir, Punjab, and into parts of Western and Central India, Gujarat, Maharashtra and Rajasthan, from the middle of the 2nd century BCE to the 4th century CE. The first Saka king in India was Maues or Moga who established Saka power in Gandhara and gradually extended supremacy over north-western India. Indo-Scythian rule in India ended with the last of the Western Satraps, Rudrasimha III, in 395 CE.
The invasion of India by Scythian tribes from Central Asia, often referred to as the "Indo-Scythian invasion", played a significant part in the history of India as well as nearby countries. In fact, the Indo-Scythian war is just one chapter in the events triggered by the nomadic flight of Central Asians from conflict with Chinese tribes which had lasting effects on Bactria, Kabul, Parthia and India as well as far off Rome in the west. The Scythian groups that invaded India and set up various kingdoms, included besides the Sakas other allied tribes, such as the Medes, Scythians, Massagetae, Getae, Parama Kamboja Kingdom, Avars, Bahlikas, Rishikas and Parada Kingdom.
The Indo-Greek Kingdom covered various parts of the Northwestern South Asia during the last two centuries BCE, and was ruled by more than 30 Hellenistic kings, often in conflict with each other.
The kingdom was founded when Demetrius I of Bactria invaded the Hindu Kush early in the 2nd century BCE. The Greeks in India were eventually divided from the Greco-Bactrian Kingdom centered in Bactria (now the border between Afghanistan and Uzbekistan).
The expression "Indo-Greek Kingdom" loosely describes a number of various dynastic polities. There were numerous cities, such as Taxila Pakistan's Punjab, or Pushkalavati and Sagala. These cities would house a number of dynasties in their times, and based on Ptolemy's Geography and the nomenclature of later kings, a certain Theophila in the south was also probably a satrapal or royal seat at some point.
Euthydemus I was, according to Polybius a Magnesian Greek. His son, Demetrius, founder of the Indo-Greek kingdom, was therefore of Greek descent from his father at minimum. A marriage treaty was arranged for Demetrius with a daughter of Antiochus III the Great, who had partial Persian descent. The ethnicity of later Indo-Greek rulers is less clear. For example, Artemidoros Aniketos (80 BCE) may have been of Indo-Scythian descent. Intermarriage also occurred, as exemplified by Alexander the Great, who married Roxana of Bactria, or Seleucus I Nicator, who married Apama of Sogdia.
During the two centuries of their rule, the Indo-Greek kings combined the Greek and Indian languages and symbols, as seen on their coins, and blended Greek, Hindu and Buddhist religious practices, as seen in the archaeological remains of their cities and in the indications of their support of Buddhism, pointing to a rich fusion of Indian and Hellenistic influences. The diffusion of Indo-Greek culture had consequences which are still felt today, particularly through the influence of Greco-Buddhist art. The Indo-Greeks ultimately disappeared as a political entity around 10 CE following the invasions of the Indo-Scythians, although pockets of Greek populations probably remained for several centuries longer under the subsequent rule of the Indo-Parthians and Kushan Empire.
The Yavana or Yona people, literally "Ionian" and meaning "Western foreigner", were described as living beyond Gandhara. Yavanas, Sakas, the Pahlavas and Hunas were sometimes described as mlecchas, "barbarians". Kambojas and the inhabitants of Madra, the Kekeya Kingdom, the Indus River region and Gandhara were sometimes also classified as mlecchas. This name was used to indicate their cultural differences with the culture of the Kuru Kingdom and Panchala.
The Indo-Parthian Kingdom was founded by Gondophares around 20 BCE. The kingdom lasted only briefly until its conquest by the Kushan Empire in the late 1st century CE and was a loose framework where many smaller dynasts maintained their independence.
The Pahlavas are a people mentioned in ancient Indian texts like the Manusmṛti, various Puranas, the Ramayana, the Mahabharata, and the Brhatsamhita. In some texts the Pahlavas are synonymous with the Pallava dynasty of South India. While the Vayu Purana distinguishes between Pahlava and Pahnava, the Vamana Purana and Matsya Purana refer to both as Pallava. The Brahmanda Purana and Markendeya Purana refer to both as Pahlava or Pallava. The Bhishama Parava of the Mahabharata does not distinguish between the Pahlavas and Pallavas. The Pahlavas are said to be same as the Parasikas, a Saka group. According to P. Carnegy, the Pahlava are probably those people who spoke Paluvi or Pehlvi, the Parthian language. Buhler similarly suggests Pahlava is an Indic form of Parthava meaning "Parthian". In a 4th-century BCE, the Vartika of Kātyāyana mentions the Sakah-Parthavah, demonstrating an awareness of these Saka-Parthians, probably by way of commerce.
The Western Satraps
The Western Satraps (35-405 CE) were Saka rulers of the western and central part of India (Saurashtra and Malwa: modern Gujarat, southern Sindh, Maharashtra, Rajasthan and Madhya Pradesh states). Their state, or at least part of it, was called "Ariaca" according to the Periplus of the Erythraean Sea. They were successors to the Indo-Scythians and were contemporaneous with the Kushan Empire, which ruled the northern part of the Indian subcontinent and were possibly their overlords, and the Satavahana dynasty of Andhra who ruled in Central India. They are called "Western" in contrast to the "Northern" Indo-Scythian satraps who ruled in the area of Mathura, such as Rajuvula, and his successors under the Kushans, the "Great Satrap" Kharapallana and the "Satrap" Vanaspara. Although they called themselves "Satraps" on their coins, leading to their modern designation of "Western Satraps", Ptolemy's Geography still called them "Indo-Scythians". Altogether, there were 27 independent Western Satrap rulers during a period of about 350 years.
The Kushan Empire (c. 1st–3rd centuries) originally formed in Bactria on either side of the middle course of the Amu Darya in what is now northern Afghanistan, Tajikistan and Uzbekistan; during the 1st century CE, they expanded their territory to include the Punjab and much of the Ganges basin, conquering a number of kingdoms across the northern part of the Indian subcontinent in the process. The Kushans conquered the central section of the main Silk Road and, therefore, had control of the overland trade between India, and China to the east, and the Roman Empire and Persia to the west.
Emperor Kanishka was a great patron of Buddhism; however, as Kushans expanded southward toward the Indian subcontinent the deities of their later coinage came to reflect its new Hindu majority.
The rise of new Persian power, the Sasanian Empire, saw them exert their influence into the Indus region and conquer lands from the Kushan Empire, setting up the Indo-Sasanians around 240 CE. They were to maintain their influence in the region until they were overthrown by the Rashidun Caliphate. Afterwards, they were displaced in 410 CE by the invasions of the Hephthalite Empire.
The Hephthalite Hunas
The Hephthalite Empire was another Central Asian nomadic group to invade. They are also linked to the Yuezhi who had founded the Kushan Empire. From their capital in Bamyan (present-day Afghanistan) they extended their rule across the Indus and North India, thereby causing the collapse of the Gupta Empire. They were eventually defeated by the Sasanian Empire allied with Turkic peoples.
The Rai dynasty of Sindh were patrons of Buddhism even though they also established a huge temple of Shiva in Sukkur close to their capital, Aror.
The Gandharan Kambojas
The Gandhara Satrapy became an independent kingdom based from Afghanistan and vied with the Tang dynasty, Tibetan Empire, the Islamic Caliphate and Turkic tribes for domination in the region.
Extent of the Karkota Empire during the reign of Lalitaditya Muktapida (8th century), according to Kalhana's Rajatarangini
. Note that Kalhana highly exaggerated the conquests of Lalitaditya.
The Karkota Empire was established around 625 CE. During the eighth century they consolidated their rule over Kashmir. The most illustrious ruler of the dynasty was Lalitaditya Muktapida. According to Kalhana's Rajatarangini, he defeated the Tibetans and Yashovarman of Kanyakubja, and subsequently conquered eastern kingdoms of Magadha, Kamarupa, Gauda, and Kalinga. Kalhana also states that he extended his influence of Malwa and Gujarat and defeated Arabs at Sindh. According to historians, Kalhana highly exaggerated the conquests of Lalitaditya.
The Kabul Shahis
The Kabul Shahi dynasties ruled portions of the Kabul valley and Gandhara from the decline of the Kushan Empire in the 3rd century to the early 9th century. The kingdom was known as the Kabul Shahan or Ratbelshahan from 565 CE-670 CE, when the capitals were located in Kapisa and Kabul, and later Udabhandapura, also known as Hund for its new capital. In ancient time, the title Shahi appears to be a quite popular royal title in Afghanistan and the northwestern areas of the Indian subcontinent. Variants were used much more priorly in the Near East, but as well later on by the Sakas, Kushans Hunas, Bactrians, by the rulers of Kapisa/Kabul and Gilgit. In Persian form, the title appears as Kshathiya, Kshathiya Kshathiyanam, Shao of the Kushanas and the Ssaha of Mihirakula (Huna chief). The Kushanas are stated to have adopted the title Shah-in-shahi ("Shaonano shao") in imitation of Achaemenid practice. The Shahis are generally split up into two eras—the Buddhist Shahis and the Hindu Shahis, with the change-over thought to have occurred sometime around 870 CE.