From the introduction:
Long held at bay by the Catholic missions of Spanish rule, the dragons of Mexico have roused from their slumber. Tempted by the promise of gold, these monsters of legend have agreed to aid Santa Anna in burning out the rebels.
But even in hot Texas, the gray days of winter are too cold for the dragons. Texian general Sam Houston knows he has mere months to strike the wyrms in their lairs before the spring sun warms them for battle. Amid the many calls for American settlers to come join the revolt against Mexico, Houston has offered bounties for the heads of dragons. Now hard-bitten dragon-slayers from across North America trek to the rough hills of the Rio Grande, armed with guns, God, and grit.