Buddhism developed in India during the life of in the Buddha in the 4th century B.C., but it took more than 1,000 years before it became the major force it is in Asia today. The Indian Emperor Asoka sent out Buddhist missionaries to southeast Asia and the Middle East in the 3rd century B.C., but it only took hold in a few places, such as Sri Lanka.
Throughout the first five centuries A.D., Buddhism slowly began to spread throughout southeast Asia, entering China, Korea, Japan and finally Tibet, where it eventually found its home. During the next 500 years, the religion continued to become more important in these countries and was eventually adopted as the official state religion. However, Buddhism began to slowly die out in India until the point where it was virtually non-existent by the middle of the 12th century.
Despite the long history of Buddhism in Asia, it really didn't begin to spread to the rest of the world until the 19th or 20th century. Due to globalization, it is now possible to find Buddhists in every corner of the globe and the religion still is a major force in society for most countries in Asia and elsewhere.