The Sukkot holiday is full of mitzvot (good deeds), including the mitzvah of the lulav, the four species. Our Sages say that the four species are similar to weapons - the lulav is similar to a sword, or perhaps a rifle, the etrog maybe to a grenade. In any event, the Sages intend to tell us that there are spiritual wars and there are physical wars, and Man in this world must confront various pests and ward them off.