Christianity in Europe:
Between 500-600 A.D. Pope Gregory I 2 , gave law to monasticism and spread the Christian gospel through Europe. He built several monasteries and parishes in this time.
Papal Christianity spread into north England and Romanized Christians converted a large option of the country by 700 A.D. Ireland wasn't Romanized and possessed its own separate form of Christianity.
Between 700-800 A.D., Christianity broke into two major factions that would become the Orthodox and Roman Catholic Church. Conversation happened in France, the Netherlands, and Belgium by Irish monks and many Irish kings converted after the yellow plague in the middle of the century. Plagues being a main reason that many countries converted to this religion. It is also of note that slavery continued despite the displeasure of the Christian church in this regard. Italy was highly the catholic denomination of Christian. It was also in this time that much of northern Germany was Christianized, partly by missionaries and partly by forced conversion.
In Spain, Catholics were allowed to worship as they liked and created a lot of art, particularly Visgothic art and art with aspects of Islam. There was a golden age for Spanish jewelry. However, late in the century Hisha I removed this tolerance and Christian's became persecuted. In the later part of the century England and Wales grew apathetic toward doctrine and many priests and nuns drank heavily or lived 'loosely'. Irish Christianity was impacted by Viking raids in the next two centuries.
Between 800-900 A.D., Christianity hit a low with heavy corruption centering in rome. However, on the edges of Christian domains more countries were being won over to the religion in Bulgaria, Serbia, Czechoslovakia, and some classes in Russia (many Russian slaves were Christian). Italian Christinaity was a mix of mythology, legend, and miracle. In Spain, there were mixed feelings and adoption of the faith after previous freedom and then persecution came slowly. Vikings from Scandinavia remained strictly unchristian and became a trouble to the world for centuries.
Islam in Middle East:
Islam primarily appeared between 600-700 A.D. It began as a military campaign and was altered to a culture after absorbing aspects of Persian culture. There was a lot of war over land between Moslums and Islamists in this time. In parts of Turkey, the Kurds were converted to Islam, unsurprising as they were related heavily to the Persians who had influenced much of Islam's creation. Islam armies took Persia in this time.
Between 700-800 A.D., Islam spread through much of the Arabian Moselem Empire (current areas of Arabia, Joran, the Mediterranean coast, Iraq, Syrian, and Iran). At one time they were popular in France and Spain. A common language was adopted which replaced several other languages and faiths. Buddhism in China was often pushed aside in preference of Islam in much of the western central area of Asia.
Between 800-900 A.D., Islam attacked Russia, and Mongolia was taken and converted by Turks. India continued for Hindu but Islam was carried to Indonesia by merchants.
Buddhism in East and Southeast Asia:
Between 600-700 A.D., the main construction of the Caves of a Thousand Buddhas took place during the T'ang Dynasty and many pilgrims flocked to see it. Tibetians became Buddhists with a war ethos and fought China. The Buddhist 'Mecca', Jokhang, was built in this century around 650 A.D., in Lhasa. China retained Buddhism but the spirituality was often matched with Confucian philosophy. There was a small resurgence of Buddhism in India for a short time but as Hinduism developed the following shrank. In Japan Buddhist philosophy was altered to better compliment Shinto, and it grew in strength but never replaced Japan's native Shinto. In Korea Buddhism flourished. In Central Asia Buddhism lost out to Islam.
Between 700-800 A.D., In India Kashmir built many magnificent Buddhist temples. The Palas of Bengal, this kept Buddhism alive when it was vanishing elsewhere in the country. Tibet formed the tantric version of Buddhism in this century. Moslems were kept out for another 2 centuries. China, Korea, and Japan maintained Buddhist beliefs. The great Buddha at Nara was built in Japan in this century.
Between 800-900 A.D. China was dominated heavily by the Turks and many Buddhist monasteries were repressed or destroyed, some monks and nuns were enslaved. Buddhism was largely destroyed in much of China in this time. Buddhism got more support in Japan. It persisted in Korea but under heavy persecution. In Cambodia Hindu and Buddhist art mixed.