Most versions begin Yahweh’s speech to Cyrus here, but some begin it with the third line in the previous verse (see the comments there). This verse uses figurative language to refer to the military successes that Cyrus will achieve with God’s help.

I will go before you and level the mountains: Yahweh will go ahead of Cyrus to make his way smooth. This figurative expression echoes the imagery in 40.3-4. The Hebrew verb rendered level has the sense of making something smooth in this context (see 40.3, where the same verb is translated “make straight”). The Hebrew term translated mountains is unusual, so its meaning is uncertain. The Septuagint has “mountains,” which most translations follow. Good News Translation says “mountains and hills,” but no other version has this reading. Revised English Bible translates it “swelling hills,” since the Hebrew word here can mean “swellings” (see the RSV footnote).

I will break in pieces the doors of bronze is a figure of speech that means God will remove anything that might prevent Cyrus’ military successes. Not only will Yahweh open city gates for Cyrus (see verse 1), but he will also destroy them. Break in pieces may be rendered “smash” or “destroy completely.” The gates in view here were either made entirely of bronze, or they were made of wood and covered with a sheet of bronze. The ancient Greek writer Herodotus recorded that Babylon had 100 bronze gates. Bronze is a brown-colored alloy, usually a mixture of copper and tin. If translators do not have a precise term for this metal, they may say “iron” or “metal.”

And cut asunder the bars of iron is parallel to the previous line. It is another figure of speech for God giving Cyrus unhindered progress on the battlefield. The bars of iron probably refers to metal bars that were used to lock the gates of the cities (compare 43.14), so Good News Translation has “their [the gates’] iron bars.”

Translation examples for this verse are:

• “I will march ahead of you
and level the mountains.
I will smash to pieces the bronze doors of the gates
and cut their iron bars.

• “I will go ahead of you
and smooth out the mountains.
I will smash down bronze [or, metal] gates
and cut in pieces their iron bars.

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 .