2DREZQ

Dragons aren't born often. (While monsters are born all the time.) There probably haven't been twenty born since the crucifixtion. Their number isn't the problem, it's that the damn things are all but immortal.
Dragons live on hate and pain and innocent blood. Certain types of fear feed them also.
They don't often choose battlefields however, unless lured there by a monster of great power. When they do find themselves on a battlefield; they bleed with the blood of men.
No matter how greviously wounded (usually after the monster is dead), Dragons cannot be killed in battle, and, not dying, their defeat is never total.

Vanished, yet not Vanquished.
The lament of the Dragon-hunter.

No matter how small they become, there seems to always be someone willing to feed the Dragon; sometimes with the blood of their own kinsmen.
Therein lies the great secret:

Dragons cannot die in battle;
they can only be starved to death.

If everyone can be convinced not to feed the Dragon, its' death comes swiftly.
Dragons can be resisted by violence and war (sometimes that is the only way).

One more thing (perhaps the most terrifying thing of all):

Dragons can be
Resurrected!