"Ancient India", like "ancient Greece", is a regional concept rather than a state. Before the arrival of the British colonists, throughout the history of the Indian region, there was indeed no native Indian dynasty that could completely piece together the Indian peninsula into a complete whole. Even the most powerful Peacock Empire and the Mughal Empire only unified most of the Indian peninsula, but the south was always a little outside the jurisdiction of the northern monarchy, such as Mysore and Tamil, that is, the southern tip of the peninsula.
So why has India been unable to twist into a rope: first, the special geographical location and situation of South Asia make it difficult for the southern tip of the Indian Peninsula to be absorbed by the north; second, the culture of race and religion is too complex, and there is basically no absolute ethnic group that occupies the main body; third, foreign invasions are too frequent, and India itself has been in a state of fragmentation for a long time, and it has no intention of completing unification.
On the surface, the geography of South Asia, the region of ancient Indian civilization, is not so complicated, especially the part of the Indian Peninsula, which is relatively flat, at least compared to East Asia. However, a closer look reveals that the geographical complexity of the Indian peninsula also has its own uniqueness, and the special geographical conditions have historically hindered the formation of India as a whole.
Ancient India
For example, the northern part of the Indian Peninsula is a vast and flat Ganga Plain, and the southern part is the vast Deccan Plateau, although the Deccan Plateau is very old and the average altitude is not high, but it is not at the same height relative to the Ganges River Basin. In particular, the further south of the Deccan Plateau, the climate becomes more humid and hot, and there are dense rainforest swamps everywhere, let alone ancient times, even if the local environment is harsh today, it is not necessarily good. For example, southern India is to northern India, just as Lingnan and Jiaotong were to the ancient Central Plains, or even more so.
In addition, on both sides of the Indian Peninsula, there are two mountains that are not too short or too short, and there are many plains on the sea side of the East and West Ghats, and these places in ancient times could rely on geographical advantages to develop into strong enough separatist forces.
India has always been known as the "ethnographic museum" and "religious museum", whether it is the population, religion, language, etc., the complexity of India is rare in the world, and the white race, yellow race, black people, etc. are distributed in India. The Indian ethnic group is really too complex, and there is no single ethnic group that occupies an absolute advantage, the largest Indians account for only 40% of the indian population today, and the Indies are also fragmented and very loose.
Before the arrival of the British, different scripts were spoken throughout India, different languages, different gods, and different sounds and different customs. Hindi is very common in North India, while in South India almost no one speaks it. When Qin Shi Huang achieved great unification, the most important thing was that "books are on the same track as the same train", but India has not really achieved it for thousands of years, and India not only lacks people like Qin Shi Huang, but also lacks such conditions.
Qin Shi Huang
The first in history to unify most of India was the famous Peacock Dynasty, but the Peacock Empire was a slave dynasty after all, and although Ashoka was strong, he did not establish an incomparably strong royal system, and there were still many powerful slave owners within the Peacock Dynasty. Until the Gupta Dynasty, the feudal system officially appeared in India, but it was still very loose, more similar to the situation in the Spring and Autumn Warring States period when the feudal system in the Central Plains was just in its infancy.
The lack of strong royal power, and the associated system to match it, prevented most of India's ancient dynasties from forming absolute control over all parts of their jurisdiction. Especially since ancient Times, under the influence of the caste system, Brahmins and many monastic groups have a very strong power, as the secular monarch of the Kshatri caste, it is really difficult to completely suppress these people.
Moreover, nature has given India a vast and flat land, and the situation of the "subcontinent" that is almost independent of the world has torn a hole in its north, the Khyber Pass. From the time when the Aryans crossed the Hindu Kush Mountains and wiped out the civilization of the Indus Valley, for thousands of years there were constantly foreign tribes entering the South Asian subcontinent from the Khyber Pass to establish royal power, and the royal power established by these foreign tribes soon repeated the same mistakes, and was destroyed by other invading ethnic groups, most of which were short-lived types and difficult to last.
The Empire of The Martial Day
After the collapse of the Northern Japanese Empire in the 7th century, Islamic forces from the Middle East continued to invade, beginning a period of intermittent northern Muslim dynasties in India that lasted for thousands of years. In the past thousand years, there have been many Muslim dynasties and many indigenous kingdoms in northern India, and many indigenous Hindu princes of India have divided one side in the central and southern regions and fought against the north. The royal power established by the Islamic forces was itself extremely limited, and no stronger than the previous indian dynasties, and neither the Delhi Sultanate nor the Mughal Empire could bring about the complete unification of the Indian peninsula.
Generally speaking, under the same civilization system, there are conditions for eventually becoming a unified country, but ancient India did not have such conditions. Since the time of the Sixteen Kingdoms, India has always been in a state of war between the various kingdoms, compared with the sub-feudal system of the Shang and Zhou Dynasties, although the princes conquered each other, they all initially respected the same son of heaven. Especially in the southern region of India, which is said to be "the land outside the country" in the words of the Central Plains, not only has a harsh geographical environment, but also has no similarities with the local ethnic groups and cultures with North India.
Over time, India has gradually developed this tradition of partition, and even in the British colonial era, there were still nearly 600 large and small states. In the history of India, whether it is the royal power established by foreign tribes or the native dynasty, its rule is very loose, and the existence of powerful clans everywhere is tacitly acquiesced, such as the Mughal Empire, which is an extremely serious internal contradiction, and if you are not careful, you will collapse, and you will not have time to do things like Qin Shi Huang. The loose and chaotic cultural system, coupled with the limitations of geographical conditions, has made India unable to cohesive for a long time, and even now, its northeast and south are still very loose.