I have always thought the anti-Christ’s war against the saints in Daniel’s 70th Week would concern gentiles that come to know Christ after the rapture. But could that scripture also apply to Jews that come to know Christ after the rapture? Will Jews also be called ‘saints’ if they accept Christ after the rapture or is this a term reserved for Gentile believers? Or reserved for the church only? If it’s reserved for the church only that means a pre-trib rapture is not possible as the A/C will be battling the church ‘saints’.
You answered your own question. If only the Church can be called saints then there cannot be a pre-trib rapture, because the anti-Christ’s war against the saints takes place at the outset of the Great Tribulation (Rev. 13:7). This verse says the anti-Christ will have the power to overcome them , but in Matt. 16:18 Jesus said the gates of Hell could not overcome the Church. Therefore other groups beside the Church must be called saints.
A saint is a holy one, one set apart for the Lord. A search for the word saint in the Bible shows Aaron, the brother of Moses, was called a saint in Psalm 106:16. In Daniel 8:13 the two angels are called saints in the KJV translation, and those who are martyred during Daniel’s 70th Week are often called tribulation saints.
From this we know that whether in the Old Testament or the New, those who are set apart for the Lord can be called saints. The term is not exclusive to the Church.