Blade of Iron — Robert Clark

Earth is invaded, not by aliens from space but by creatures of what we thought were fantasy. Our technology fails, making the swords and spears of the invaders far more effective than guns unable to fire, planes unable to fly, or motionless tanks. Resistance continues around the world, as not just humans but virtually every living thing on earth battle the invaders in what seems a hopeless war. A handful of humans may have the ability and the tool, an ancient, iron-bladed dagger, to defeat the creatures from Fairie. The Beils and their friends must fight their way to Washington, gathering allies as they go, to confront the leader of the invasion, but reaching Washington won't guarantee success. Even if they win through against incredible odds, carrying the Blade of Iron to where it is needed, will they be forced to send a four year old girl against the leader of the invaders with nothing but the dagger to use against him?