In 1953 in Jordan and Saudi Arabia, a new revivalist movement appeared: Hizb al-Tahrir al-Islami ("The Islamic Liberation Party"). The party's founders were refugee Palestinians led by Sheikh Taqiuddin an-Nabhani Filastini. The leader in 2004 was Sheikh Abdul Qadeem Zaloom, also a Palestinian and a former professor at al-Azhar University.
Sheikh Nabhani was a graduate of al-Azhar university, a schoolteacher, and a religious judge (qadi) before he was forced to leave Palestine after the 1948 Arab-Israeli war.
At the outset of the twenty-first century, the group was most active in Central Asia (Uzbekistan, Kyrgyzstan, and Tajikistan). There its mission was to unite Central Asia, Xinjiang Province in China, and in the long run all Muslims worldwide (the umma) under a new caliphate modeled after the Rashidoon period that followed the Prophet Muhammad's death. (Turkey's ruler Ataturk had abolished the caliphate in 1924.)
HT was influenced by the Wahhabis' uncompromising opposition to Shiism and to Sufism. But, HT differed from the Wahhabis in that it sought to bring about change peacefully while the Wahhabis saw a place for militant jihad.
HT, banned from Middle Eastern countries, began putting down roots in European states. London became a major organizational hub for the group. Turkey, Central Asia, and Western Europe were the three areas where the group focused most of its energy. Germany banned the group in 2003 finding it in violation of that country's laws against anti-Semitism. The suspected bombers in the July, 2005 attacks in London were members of a splinter group associated with HT. (more on Muslims in Europe)
Sources:
Zeno Baran, "Fighting the War of Ideas," Foreign Affairs, November/December, 2005, 68-78.
Ahmed Rashid, Jihad: The Rise of Militant Islam in Central Asia (New Haven: Yale University Press, 2002)
More:
Jane Perlez, "London Gathering Defends Vision of Radical Islam," New York Times, Aug. 6, 2007 (on HT's call for restoration of the caliphate).