Revelation 12:17 testifies that there is a remnant descendant of the woman. In order to know who the woman's remnant descendants are, we need to know who the woman of 12:1 is. As we have already explained, the woman with the crown of twelve stars is a metaphor for the members of the early church who received the Holy Spirit of Yehoshua. You can read more about this in the links below.

http://godnara.egreef.kr/bbs/board.php?bo_table=cs_notice_eng&wr_id=152&page=4 

And the red dragon with seven heads and ten horns that tried to kill Yehoshua, represented as a baby, is a metaphor for Satan, who was represented in this way by the seven angels who rebelled against God and the ten subordinate angels who followed their instructions. After being expelled from heaven, Satan created a religious organization called Catholicism to torment God's people, which you can read more about at the link below. 

http://godnara.egreef.kr/bbs/board.php?bo_table=cs_notice_eng&wr_id=151&page=4 

Satan, who had been cast out of heaven, persecuted the saints of the early church who had received the Holy Spirit of Yehoshua. The saints, who were likened to women, hid from the dragon for 1260 days, and the dragon spat out a lot of water from its mouth to kill the woman. But the earth helped the woman and swallowed the water that the dragon spat out; but this was written as a parable. Hiding from the dragon for 1260 days was a prophecy that God's people would be under the power of the dragon for 1260 years. Also, the water the dragon vomited out to kill the woman was not real water, but a false doctrine created by Satan.

Catholicism created the doctrine of the Inquisition and the witch hunt for 1260 years from AD 538 to 1798, killing and harassing God's people. They also changed the Ten Commandments and enforced idolatry. Just as the water of life springs up from the stomach when God's people receive the Holy Spirit, the water that Satan, represented by the dragon, spews out also refers to numerous doctrines created by Catholicism. 

But a force rose up against Catholicism, and they were the Reformers, who realized that Catholic doctrine was wrong and fought against it. The Bible likens them to a land that has been swallowed up by a river, and the dragon is enraged and fights the remnant of the woman on the beach, and the remnant of the woman is a metaphor for the Reformers.

[Revelation 12:17~18] This made the dragon very angry with the woman. So she went to war with the rest of the children. They obey God and are faithful to what Jesus did and taught. The dragon was standing on the beach. 

So who was the winner of that battle? Reformers, represented by remnant women, and Catholicism, ruled by dragons, waged a fierce religious war. In this regard, the Bible testifies: 

[Revelation 13:1~8] And the dragon stood on the shore of the sea. And I saw a beast coming out of the sea. He had ten horns and seven heads, with ten crowns on his horns, and on each head a blasphemous name...(7) He was given power to make war against the saints and to conquer them. And he was given authority over every tribe, people, language and nation. All inhabitants of the earth will worship the beast—all whose names have not been written in the book of life belonging to the Lamb that was slain from the creation of the world. 

According to biblical evidence, Catholicism, ruled by the dragon, had the power to fight and overcome the saints, so the Reformers, who were likened to the descendants of a woman, were defeated and killed in battle with the dragon and served the dragon. The early Reformers turned to God to fight the Catholics, but they also practiced witch hunts and the Inquisition and copied many of the doctrines that the Catholics had started, such as tithing and cross idols. Thus, the Bible testified that all the people living on the earth worshiped the red dragon.

So the woman's remaining descendants are an analogy for the Reformers who fought against Catholicism.