Their arrows are sharp pictures an army ready for attack, with its arrows sharpened.

All their bows bent suggests that they already have arrows placed in their bows ready to fire them. When a bow is not in use, it is stored without any tension in order to preserve its strength and flexibility. A soldier or hunter will pull a bow tight and fit the string into position when he wants the bow to be ready for use. All their bows bent may be better expressed as “all their bows are strung and ready.” In cultures where bows and arrows are not known, or not known to be weapons of war, translators may substitute a more general expression for the first two lines, for example, “their weapons are at the ready.”

Their horses’ hoofs seem like flint: This is the first of several similes in verses 28-30. The hoofs of the enemy’s horses are as hard as flint, which is a very hard stone. Hoofs should be hard so that the horses can run over all kinds of ground without being harmed. Horses were used to pull chariots (see the next line), but soldiers also rode them (see the comments on 2.7). For this line translators may say “the hoofs/feet of their horses are as hard as stone.”

And their wheels like the whirlwind: Grammatically speaking their wheels would refer to the horses’ wheels, but obviously it is the wheels of the enemy’s chariots, pulled by the horses, that are in focus. This may need to be made clear in some languages by saying “their chariot wheels” (Good News Translation, New International Version, Revised English Bible; similarly Contemporary English Version). Like a whirlwind compares the advance of the chariots to a frightening tornado that picks up and carries off everything in its path (see Job 27.20; Pro 1.27). So this line pictures rapidly advancing war chariots that threaten utter devastation.

Alternative translation models for this verse are:

• Their arrows are sharp and their bows at the ready,
their horses’ hooves are as hard as stone,
the wheels of their war chariots turn fast like the whirlwind.

• Their bows are at the ready, set with sharp arrows,
like hard flint stone are their horses’ hoofs,
and like a tornado are their chariot wheels.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .