[Ayyfjicg]

al-Salamu `Aleykum,

Allah (swt) says:

Let not believers take disbelievers as allies rather than believers. And whoever [of you] does that has nothing with Allah, except when taking precaution against them in prudence. And Allah warns you of Himself, and to Allah is the [final] destination. (Quran 3:28)

MEANING,

If a believer is living in a country full of Kouffar, and he is threatened by the Kouffar, then he can Lie to them and claim that he is not a Muslim BUT in his heart he firmly believes in Allah (swt).
This is called "Taqqiyah".

So if there is fear of being killed, or having one of your limbs cut, or fearing for your wealth or family, then you can lie with your tongue to push the harm away from you, but in your heart you are still a believer.
Taqqiyah is only done with the tongue and NOT with the actions according to Ibn `Abbas (ra) and Moujahid (rah).

One of the Prophet's (SAWS) close companions was called `Ammar (ra), and Islam was still new at the time, and the Muslims were of little numbers and they had no strength to defend themselves, so `Ammar (ra) and his family were taken as captives by the Kouffar, and the Kouffar started telling `Ammar (ra) to reject the faith of Muhammad (SAWS) and leave Islam, but he refused, they started torturing him and torturing his family in front of him, finally he told them that he has rejected Islam so they left him.
He then went to complain to the Prophet (SAWS), he told him the story and the Prophet (SAWS) asked: "When you said it, did you have strong faith in Allah in your heart?" `Ammar (ra) said:"Yes" So the Prophet (SAWS) then told him: "If they do it again then do what you did."

Means he allowed him to utter Kufr with his tongue in order to save his life. However, the scholars of Islam say that the one who does not succumb to the pressure of society and keeps declaring his faith in Allah (swt) even when harmed, gets more reward.

For example Bilal ibn Raba (ra) was a black slave and his masters tortured him because he embraced Islam, they tied him up then placed a big hot rock to crush his body, they ordered him to leave the religion but he refused and kept saying "God is only one!".
Another example is the companion Ibn Habib al-Ansari (ra), when he was caught by the false-prophet Musaylamah al-Kazzab, Musaylama ordered him to declare that he is also a Prophet just like Muhammad (SAWS), but ibn Habib refused and he kept saying that Sayyiduna Muhammad (SAWS) was the seal of prophets, the cursed Musaylamah had to cut him alive piece by piece.

I hope this indirectly answers your question.

Salam `Aleykum,