They shall run like mighty men; they shall climb the wall like men of war; and they shall march every one on his ways, and they shall not break their ranks:

Wesley's Notes

2:7 Their ranks - This skill in ordering and the steadiness in keeping under, exactly like trained soldiers, foretells the terror and strength of both the armies signified by these locusts, and of the locusts themselves.

Jamieson-Fausset-Brown Bible Commentary

7-9. Depicting the regular military order of their advance, "One locust not turning a nail's breadth out of his own place in the march" [Jerome]. Compare Pr 30:27, "The locusts have no king, yet go they forth all of them by bands."

Matthew Henry's Concise Commentary

2:1-14 The priests were to alarm the people with the near approach of the Divine judgments. It is the work of ministers to warn of the fatal consequences of sin, and to reveal the wrath from heaven against the ungodliness and unrighteousness of men. The striking description which follows, shows what would attend the devastations of locusts, but may also describe the effects from the ravaging of the land by the Chaldeans. If the alarm of temporal judgments is given to offending nations, how much more should sinners be warned to seek deliverance from the wrath to come! Our business therefore on earth must especially be, to secure an interest in our Lord Jesus Christ; and we should seek to be weaned from objects which will soon be torn from all who now make idols of them. There must be outward expressions of sorrow and shame, fasting, weeping, and mourning; tears for trouble must be turned into tears for the sin that caused it. But rending the garments would be vain, except their hearts were rent by abasement and self-abhorrence; by sorrow for their sins, and separation from them. There is no question but that if we truly repent of our sins, God will forgive them; but whether he will remove affliction is not promised, yet the probability of it should encourage us to repent.