The whole world is a suitable location for the Islamic call. But since the people in the Muslim countries have already embraced Islam, it is necessary that the call start there. The Arab countries are the most suitable location to start carrying the call because these countries, which constitute part of the Muslim world, are inhabited by people who speak the Arabic language, which is the language of the Qur'an and Hadith, and is an essential part of Islam and a basic element of the Islamic culture. Hizb ut-Tahrir began and started to carry the Islamic call within some of the Arab countries. It then proceeded to expand the delivery of the Islamic call naturally until it began to function in many Arab countries and also in non-Arab Muslim countries as well. Hizb ut-Tahrir seeks the re-establishment of the Islamic Khilafah "Caliphate" (Caliphate) in the Islamic World.