Taqiyya, lying to help the caliphate,

In the Middle East, but especially Islam, the concealment of belief, as a method of self-protection. Taqiyya is allowed, and performed, when necessary to avoid death or injury to oneself or other Muslims. Taqiyya is mainly considered as a part of Shi’i theology or modern-day Islamism.
Taqiyya may be translated with ‘fear’ and ‘caution’. It is closely related to the term katm or kitman, ‘concealment’. Taqiyya is in many cases linked with regulations of how Muslims should act with non-Muslims.
The rules concerning the true intention of taqiyya are strict, and abusers of taqiyya will be punished by God.
The permission to conceal the faith is believed to be admitted by the Koran:

Koran sura 16: The Bee
108 … unless it be one who is forced and whose heart is quiet in the faith…

Koran sura 3: Imran’s house
27 … If you hide that which is in your breasts, or if you show it, God knows it…

Some interpret Muhammad to have performed taqiyya, too, when migrating to Yathrib (later Madina) instead of risking his life staying in Mecca. This interpretation may seem doubtful, but has importance with Muslims in order to legitimize taqiyya. It must be stressed that the two Koran verses above seem to allow acts of taqiyya; they even seem to allow it indiscriminately, meaning that it is up to the individual to decide when it is fit to conceal all or parts of his/her faith.

http://i-cias.com/e.o/taqiyya.htm