The Remnant, by Tim LaHaye and Jerry B. Jenkins, (Left Behind Series, Book 10) from Books In Motion.com

Rayford Steele and the beleaguered Tribulation force scattered across the globe are battling on against evil on the brink of Armageddon. All pretense is gone, even on the part of the Antichrist, as the planet hurtles toward the last battle and ultimate showdown between good and evil. Carpathias enemies are seemingly right where he wants them, trapped at Petra with no way out. No one can survive his diabolical attack without some sort of a miracle. The Tribulation Forces aliases and even their Strong Tower safe house have been compromised, forcing Rayford Steele, Buck Williams, and all the forces members to flee for their lives while trying to maintain their covert and unrelenting opposition to the Antichrist....