Thou breakest the ships of Tarshish - Calmet thinks this may refer to the discomfiture of Cambyses, who came to destroy the land of Judea. "This is apparently," says he, "the same tempest which struck dismay into the land-forces of Cambyses, and wrecked his fleet which was on the coasts of the Mediterranean sea, opposite to his army near the port of Acco, or the Ptolemais; for Cambyses had his quarters at Ecbatana, at the foot of Mount Carmel; and his army was encamped in the valley of Jezreel." Ships of Tarshish he conjectures to have been large stout vessels, capable of making the voyage of Tarsus, in Cilicia.
Thou breakest the ships of Tarshish - On the ships of Tarshish, see the notes on Isaiah 2:16. The allusion to these ships here may have been to illustrate the power of God; the ease with which he destroys that which man has made. The ships so strong - the ships made to navigate distant seas, and to encounter waves and storms - are broken to pieces with infinite ease when God causes the wind to sweep over the ocean. With so much ease God overthrows the most mighty armies, and scatters them. His power in the one case is strikingly illustrated by the other. It is not necessary, therefore, to suppose that there was any actual occurrence of this kind particularly in the eye of the psalmist; but it is an interesting fact that such a disaster did befall the navy of Jehoshaphat himself, 1 Kings 22:48: “Jehoshaphat made “ships of Tarshish” to go to Ophir for gold; but they went not: “for the ships were broken” at Ezion-geber.” Compare 2 Chronicles 20:36-37. This coincidence would seem to render it not improbable that the discomfiture of the enemies of Jehoshaphat was particularly referred to in this psalm, and that the overthrow of his enemies when Jerusalem was threatened called to remembrance an important event in his own history, when the power of God was illustrated in a manner not less unexpected and remarkable. If this was the allusion, may not the reference to the “breaking of the ships of Tarshish” have been designed to show to Jehoshaphat, and to the dwellers in Zion, that they should not be proud and self-confident, by reminding them of the ease with which God had scattered and broken their own mighty navy, and by showing them that what he had done to their enemies he could do to them also, notwithstanding the strength of their city, and that their “real” defense was not in walls and bulwarks reared by human hand, anymore than it could be in the natural strength of their position only, but in God.