Adam Clarke on Joel 1:9

Prepare war - Let all the enemies of God and of his people join together; let them even call all the tillers of the ground to their assistance, instead of laboring in the field; let every peasant become a soldier. Let them turn their agricultural implements into offensive weapons, so that the weak, being well armed, may confidently say, I am strong: yet, when thus collected and armed, Jehovah will bring down thy mighty ones; for so the clause in Joe 3:11 should be rendered.