The shield of his mighty men is made red, the valiant men are in scarlet: the chariots shall be with flaming torches in the day of his preparation, and the fir trees shall be terribly shaken. The shield of his mighty men is made red - These things may refer to the war-like preparations made by the Ninevites: they had red shields, and scarlet or purple clothing; their chariots were finely decorated, and proceeded with amazing rapidity.
The fir trees shall be terribly shaken - This may refer to the darts, arrows, and javelins, flung with destructive power.