These republican states which flourished upto Gupta period of Indian history, disappeared in the 4th century A. D. For this, perhaps the Imperial Guptas were mainly responsible.
The Persian, the Greeks, Kushans from Central Asia over ran Northern India. In 327 B.C. Alexander from Macedonia crossed the Afghanistan and advanced as far as river Beas in 326 BC. Alexander met stiff resistance in Punjab and river Beas was flooded, and his soldiers refused to go further so he could not cross Beas and returned back to Macedonia and died on the way at Babylon in Afghanistan.
After departure of Alexander Chandragupta Maurya gained Magdha in 324 B.C. with help of Chanakya who is known as Kautilya and Vishnugupta.
Chandragupta fought a battle against Alexander’s governor. He made an alliance with the Himalayan chief Parvataka. He tried to penetrate into the inner hills of Himalayas. There is mention in Mudrarakshasa that he was opposed by a coalition of five kings, among whom the name of Chitravarma of Kuluta is mentioned.
Ashoka the grandson of Chandra Gupta extended his boundaries in the Himalayan region and erected many stupas in the region. One of these Stupas was in Kullu Valley mentioned by Huien Tsang. Ashokan rock edicts was found in Kalsi. He was a staunch Buddhist. He sent group of Buddha monks headed by Majjhima. Other monks were Kasapagotta, Dundhibissara, Sahadeva and Mulakadeva to spread Buddhism in Himalayan regions.
Mauriyan Dynasty was followed by the Sunghas dynasty. They could not keep these tribal republic under their control. During Sunghas reign local republics of Himalaya became free and issued their own coins. Sunghas were followed by Kushana. Kanishka was the greatest ruler of this dynasty. He was a staunch Buddhist. Kanishka’s 40 copper coins were found on the Kalka- kasauli road with 382 copper coins of Wema Kadphises.
In the 4 century AD Guptas were emerged as power with its capital at Patliputra. The Gupta empire was founded by Shrigupta.
The great king of his dynasty was Samudragupta. He is also known as Napoleon of India and kavi Raj. His achievement has been mentioned by his minister of war, Harisena on Ashoka pillar at Allahbad. Himalayan rulers have accepted Samudragupta’s paramountncy without having any armed conflict. Samudra Gupta never felt the need of picking up arms against them.
Other famous ruler of Guptas dynasty was Chandragupta ll. The plot of Vishakhadatta’s play Devichadraguptam is the story related to Ramgupta his wife Druva Devi and Chandragupta-ll. Saka King defeated Rama Gupta and took Dhruva Devi with him. Bana Bhatta has also mentioned this event in his book Harshacharita. Chandragupta ll killed Saka king in order to protect her sister-in-law. He continued the task of conquest and empire expansion.
During 4th century to 6th century many changes took place in political conditions of Himalayan states. Some old states disappeared and new appeared.
Audumbara republic also come to an end in 4th century. Kuninda republic fragmented into many small kingdoms with the rise of Guptas power in the 4th century AD like Brahmpura, Govisana and Kartipur. The name of karitpur is found mentioned in the Allahabad inscription. The Kulutas probably had encroached on their land.
The Trigarta people seem to have faced foreign aggression and Guptas subjugation. During this time two new powers i.e. Bushahr and Sirmaur came into existence. In the 6th century, in the area of upper Ravi Chamba was founded by Meru Varman. Its capital was Brahmpura (modern Bharmaur).
In the middle of the 5th century AD a central Asian tribe, the Hunas accompanied by Gujjars entered Punjab and moved towards Yamuna valley. Their chief was Toramana and he was succeeded by his son Mihirakula. He was very cruel. In 520 AD he was defeated at kahru (Multan) by united forces of Baladitya of Magadha and Yashodharman of Malva. He was forced to retire to Kashmir.
After the Guptas Empire and before emergence of Harsha except Kangra and kullu, the whole of Himachal Pradesh was divided into small Apthakurai ruled by Raja, Rahun ruled by Rana and Thakurai ruled by Thakurs.
Harsha ascended the throne in 606 AD and the central power now shifted first from Patliputra to Thaneshwar and then to Kanauj. He established a very powerful empire in India.
The great Chinese pilgrim Hiuen-tsang visited India during Harsha’s reign and stayed here for 13 years (AD 630-644). In 635 AD he visited Jalandhara remained there as a guest of raja Utitas. He mentioned temples of devas, all belonged to the Pahsupati. After spending four months at Jalandhra he went to Kullu and called it ku-lu-ta (kuluts). He visited Lo-u-Lo (Lahaul) also and stayed for some time, and then went to Surughna (Sirmaur) with the monk JayaGuptam. In the seventh century a new branch of Buddhism called Vajrayana emerged with its center in Eastern India.
Niramand copper plate is founded in kullu district . It is estimated that it belongs to 7th century AD, the donor of this plate call himself Mahsamanta. The name mentioned on the plate is of Maharja Vermasen and his successor.
In the early century of Christian era, a pre Buddhist Hindu dynasty with the surname of Sena had ruled in the spiti.