Also he strengthened himself, and built up all the wall that was broken, and raised it up to the towers, and another wall without, and repaired Millo in the city of David, and made darts and shields in abundance.

He built up also with great diligence all the wall that had been broken down, and built towers upon it, and another wall without: and he repaired Mello in the city of David, and made all sorts of arms and shields:

And he strengthened himself, and built up all the wall that was broken down, and raised it up to the towers, and built another wall outside, and fortified the Millo of the city of David, and made darts and shields in abundance.

And he strengtheneth himself, and buildeth the whole of the wall that is broken, and causeth it to ascend unto the towers, and at the outside of the wall another, and strengtheneth Millo, in the city of David, and maketh darts in abundance, and shields.

Then he took heart, building up the wall where it was broken down, and making its towers higher, and building another wall outside; and he made strong the Millo in the town of David, and got together a great store of all sorts of instruments of war.

And he took courage, and built up all the wall that was broken down, and raised it up to the towers, and another wall without, and strengthened Millo in the city of David, and made weapons and shields in abundance.

He took courage, and built up all the wall that was broken down, and raised towers upon it, and the other wall outside, and strengthened Millo in the City of David, and made weapons and shields in abundance.

Also, acting industriously, he built up the entire wall that had been broken apart. And he constructed towers upon it, and another wall outside it. And he repaired Millo, in the City of David. And he made all kinds of weapons and shields.

The breaches in the wall of Jerusalem were not entirely due to the old hostility of Joash (marginal reference); but may have been caused either by neglect and carelessness in the reign of Ahaz 2 Chr. 28, or by the simple process of natural decay. Hezekiah pulled down houses for the purpose of his repairs Isaiah 22:10.
On Millo, see the marginal references notes.

Raised it up to the towers - He built the wall up to the height of the towers, or, having built the wall, he raised towers on it.

Also he strengthened himself, and built up all the wall that was broken, and raised [it] up to the towers, and another wall without, and repaired (a) Millo [in] the (b) city of David, and made (c) darts and shields in abundance.
(a) He made a double wall.
(b) Read (2-Samuel 5:9).
(c) Some read, swords or daggers.

Also he strengthened himself,.... In the Lord his God, and fortified his city, and put it in the best manner of defence he could:
and built up all the wall that was broken; which was broken from the gate of Ephraim to the corner gate by Joash king of Israel; and though it might have been repaired by Uzziah, it might again be broken down in the times of Ahaz, by Pekah, king of Israel, or some other enemy, see 2-Chronicles 25:3.
and raised it up to the towers; from the corner tower to the tower of the gate of Ephraim, which, as before observed, had been broken down:
and another wall without; a second wall, either all around the city, or at such a part of it which was weakest; Josephus (z) says the city of Jerusalem had three walls about it:
and repaired Millo in the city of David; a wall on the north side of the city:
and made darts and shields in abundance; darts to cast from the walls of the city, to annoy the enemy with, and shields to defend them from those of the enemy.
(z) De Bello Jude. l. 5. c. 4. sect. 3.

he strengthened himself--He made a careful inspection of the city defenses for the purpose of repairing breaches in the wall here, renewing the masonry there, raising projecting machines to the towers, and especially fortifying the lower portion of Zion, that is, Millo, "(in) the original city of David." "In" is a supplement of our translators, and the text reads better without it, for it was not the whole city that was repaired, but only the lower portion of Zion, or the original "city of David."

The fortification of Jerusalem. יתחזּק, he showed himself strong, courageous, as in 2-Chronicles 15:8; 2-Chronicles 23:1. And he built the whole wall which was broken, i.e., he strengthened it by building up the breaches and defective places; cf. Isaiah 22:9. The words על־המּגדּלות ויּעל are obscure, since the translation "he mounted on the towers" has no meaning. But if יעל be taken as a Hiph., "he caused to ascend upon the towers," the object is wanting; and if we supply walls, it is arbitrary, for we might just as well suppose it to be machines which he caused to be carried to the top of the towers for defence against the enemy (2-Chronicles 26:15). The lxx have wholly omitted the words, and the translation of the Vulg., et exstruxit turres desuper, appears to be only a guess, but is yet perhaps correct, and presupposes the reading מגדּלות עליה ויּעל, "and brought up upon it towers," in favour of which Ewald also decides. This conjecture is in any case simpler than Bertheau's, that על ויעל is a false transcription of ועליה: "he built the whole wall, and towers upon it, and outside was the other wall," and is therefore to be preferred to it. The "other wall" enclosed the lower city (Acra). This, too, was not first built by Hezekiah; he only fortified it anew, for Isaiah 22:11 already speaks of two walls, between which a body of water had been introduced: see on 2-Chronicles 32:30. He fortified also the Millo of the city of David (see on 1-Chronicles 11:8), and supplied the fortifications with weapons (שׁלח, a weapon of defence; see on Joel 2:8) in multitude, and with shields; cf. 2-Chronicles 26:14.