Starting in the Sapta-Sindhu (the seven rivers) plains, the northern spread of Sanskrit during the Rigvedic phase covered areas from Pakistan in the west, Kashmir in the north, western UP in the east, and Gujarat in the south. By the time of the remaining three Vedas, the northern spread of Sanskrit had extended to parts of Afghanistan, lower Central Asia, and the foothills of Nepal. The spread east and south was more dramatic, with Sanskrit reaching the Gangetic plain up to Bihar and central India, north of the tribal belt. As mentioned earlier, due to a deliberate avoidance of written records, most conjectures about the dating and geographical spread of Sanskrit rely on secondary and deductive archaeological evidence linked to the arrival and spread of the Aryans.
In the next wave, during the post-Gupta period, Sanskrit spread up to Bengal in the east and traveled along the eastern coast down to southern India. The Pallavas played a pivotal role in establishing Sanskrit's foothold in southern India. Sanskrit was the primary language of instruction at ancient centers of learning like Takshashila, Nalanda, and Vikramshila, though courses were also offered in Pali, Tibetan, Chinese, and Greek. By this time, the core geographical area of Sanskrit's influence covered the entirety of India, Sri Lanka, Nepal, Pakistan, and Afghanistan. The further spread of Sanskrit, along with other elements of ancient Indian culture, was facilitated by trade in East Asia and the spread of Hinduism and Buddhism. This penumbra of influence extended to Central Asian regions along the Silk Road, as well as China, Tibet, Japan, Korea, Cambodia, Vietnam, Thailand, Malaysia, and Indonesia. In addition to scholars from these regions, Persian and Arab scholars also studied Sanskrit in ancient times for the wealth of knowledge and ideas which were then transmitted onwards in Arabic further west. For a language that was never spoken as a vernacular, this was an impressive achievement. It stands as a testament to Sanskrit's role as the language of choice for scholars, creators, and thinkers, leaving an enduring footprint across nations, languages, and cultures over a significant period in human history.
With the decline in political patronage, as described earlier, Sanskrit entered a long period of gradual decay. In regions of secondary influence, Sanskrit was almost entirely lost, while in its core areas, it became concentrated among fewer and fewer individuals with a diminishing of resources available and consequently prospects of further growth. This led not only to the cessation of authoring of new works in Sanskrit but also to a significant loss of its existing body of work. Following the trend seen in the migration of native Indian languages, Jainism, Buddhism and ancient Indian classical music, the role of preservation of Sanskrit increasingly shifted to southern India as its presence, quality, and education declined in the North. Both schools of Vedic learning and the creation of new works in Sanskrit in science, mathematics, literature and arts continued in the South.
During the British era, a handful of enlightened archaeologists, historians, and philosophers from Europe and later America discovered Sanskrit and its vast corpus, spanning a wide variety of subjects, genres, and literary forms. This marked the first time the splendor of Sanskrit was revealed to the Western world. This, in turn, inspired a new generation of Indians to revive and reclaim Sanskrit, restoring its lost glory. Today, Sanskrit is a subject of study and research worldwide. Exciting new dimensions are being uncovered using advanced tools and technology, new archaeological findings, and the re-examination of old texts, supported by more scientific and credible theories.