Rom 10:17 So then faith cometh by hearing, and hearing by the word of God.
Rom 10:18 But I say, Have they not heard? Yes verily, their sound went into all the earth, and their words unto the ends of the world.
Something else to think about.
Revelation 7:9-10, 13-14 "After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;
10) And cried with a loud voice, saying, Salvation to our God which sitteth upon the throne, and unto the Lamb."
13) And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
14) And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
During the Tribulation the gospel will be preached to all nations either by people or even angels (see Rev. 14). In the above passage we see that out of every nation there will be saved people during the Tribulation.
The light of the gospel shines the brightest during the darkest times.