Tantrayana, a new tradition of Buddhism, started developing from the 7th century AD, and was radically different from the earlier traditions in several important ways. Tantrayana, the Vehicle of the Text, is also known as Mantrayana, the Vehicle of Spells, or the Vajrayana, the Adamantine Vehicle. The Tantrayana or Vajrayana is actually a subset of the Mahayana Buddhism. The Tantrayana Buddhists themselves often classify their school as the final stage in the evolution of Indian Buddhist theory which they enumerate as Hinayana, Mahayana and Vajrayana. The Tantrayana Buddhism facilitates an accelerated path to enlightenment to be achieved through the use of tantra techniques, which are practical aids to spiritual development and esoteric transmission.

Whereas earlier schools of Buddhism provide ways to achieve Nirvana over the course of many lifetimes, the Tantrayana school makes full enlightenment or Buddhahood possible in a shorter time frame, or perhaps, in a single lifetime. While the goal of the Mahayana and Vajrayana is the attainment of Buddhahood, the goal for Tantrayana or Theravada practice is liberation from the cycle of rebirth in Nirvana.  

The Speed Up Technique - Tantric Practices  
The chief factor in the Vajrayana concept of Buddhism is tantric practices. The tantric path emphasises on the 'use of result as the path', which means that instead of placing full enlightenment as a goal far away in the future, one should try to identify with the enlightened body, speech and mind of a Buddha through symbolism and visualisation. The Tantric Buddhism gives more importance to secrecy in order to avoid the
practices from harming oneself and others without proper guidance. The tantric practices may at first appear as ritualistic nonsense, but can only be practiced on the basis of a thorough understanding of Buddhist philosophy and traditions.

The Tantric practices consist

1.  Repetition of special ritual phrases or mantras.
2.  Use of an extensive vocabulary of visual aids like cosmic mandala diagrams which is used as a path to spiritual enlightenment.
3. Use of numerous Yoga techniques.
4.  Use of ritual objects such as the vajra and bell (ghanta), hand-drum (damru), and many other symbolic tools and musical instruments.
5. IImportance of a teacher (guru)-disciple (shishya) relationship (parampara).
6. Use of specialised rituals rooted in the Vajrayana cosmology and beliefs.

Sex is symbolic in the Buddhist tantra, though one's sexual energy can be transformed into a blissful consciousness to be directed towards achieving wisdom and enlightenment through the act of sexual intercourse. Vajrayana iconography treats sexual symbolism commonly, where it basically represents the marriage of wisdom and compassion. Besides, the Tantrayana has also developed a rich and complex variety of meditation techniques.

Esoteric Transmission or Initiation
The very next speed up technique of the Tantrayana tradition is its esoteric transmission or initiation. Esoteric means the transmission of certain accelerating factors, which only occurs directly from teacher to student during an initiation and cannot be simply learned from a book.

Here, the techniques have no validity outside the teacher-student lineage. Since these techniques are highly effective, a practitioner can harm himself physically and mentally if he does not practice these techniques properly. Therefore, the practice should be kept secret outside the teacher-disciple relationship.

The Spread of Tantrayana
Vajrayana or Tantrayana exists in the form of two major sub-schools:

1. Tibetan Buddhism in Tibet, Bhutan, northern India, Nepal, south-west China, Mongolia and Kalmykia (the only Buddhist state of Europe.
2.  Shingon Buddhism in Japan.

India
Tantrayana developed in Bengal and Orissa and flourished during the period of Buddhism's decline in India from 8th to 13th century AD. However, there are differing views regarding the origin of Tantrayana or Vajrayana. Some claim that it began in Udyana - the modern day Swat valley in Pakistan, while the others say that it originated in the southern India. In the Tibetan tradition, it is claimed that the historical Shakyamuni Buddha taught tantra, but as these are 'secret' teachings outside the teacher/disciple relationship, they were penned down long after the Buddha's other teachings, known as Sutras.
The earliest texts related to Tantrayana appeared around the early 4th century. In northern India, the Nalanda university had by now became a centre for the development of Tantrayana theory. The Tantrayana practices led the other practices throughout the 11th century in India, but started declining after this period.
The Tantrayana Buddhism had mostly died out in India by the 13th century AD when its practices merged with Hinduism, and both tantric religions experienced pressure from the rising importance of Islam. By that time, the vast majority of the practices were also made available in Tibet, where they still remains.
A number of Tibetan exiles fled the oppressive anti-religious rule of the Communist Chinese and to establish Tibetan Buddhist communities in the northern India in the 20th century. They still remain the primary followers of the Tantric Buddhism in India and the entire world.
China
The Tantrayana Buddhism reached northern China from India via the Silk route in the first half of the 7th century AD. It was during this period that the Buddhism was on its peak in China. The Tang capital at Chang'an (Modern Xi'an) had become an important centre for the Buddhism studies and that is why, Tantrayana received great attention over here.

Japan
The emperor Kammu of Japan asked the monk Kukai to retrieve the latest Buddhist knowledge from China in 804 AD. The monk absorbed and synthesised the Tantrayana Buddhism into a version and took it to Japan, where he founded the Shingon school of Buddhism, which preached the basics and depth of Tantrayana.

Tibet and other Himalayan Kingdoms
The Indian saint, Padmasambhava travelled from Afghanistan to Tibet to bring Tantrayana Buddhism to Tibet on the request of the Tibetan king, and led to the foundation of the Nyingma school in Tibet. Later in the 11th and 12th century AD, another important transmission led to the lineage of Atisa, Marpa and Brogmi, which gave rise to other schools of Tibetan Buddhism - Kagyupa, Kadampa, Sakyapa and Gelukpa, the school of Dalai Lama.