The teachings of the Buddha are a treasury of wisdom that has been passed down from teacher to student for over 2,500 years. Many styles of teaching have developed, but all of the schools of Buddhism present the means to realize the awakened state of mind. And all of them emulate the example of the Buddha, the Awakened One. This is a very important point to realize in the context of presenting tantra, or the vajrayana teachings of the Buddha. It is both dangerous and fruitless to attempt to practice tantra without first establishing a firm ground in the basic Buddhist teachings.
From Journey without Goal: The Tantric Wisdom of the Buddha by Chögyam Trungpa, page 1.