John Gill

Their roaring shall be like a lion,.... When engaged in war, just seizing on their prey. The phrase denotes their fierceness and cruelty, and the horror they should inject into the hearts of their enemies: they shall roar like young lions; that are hungry, and almost famished, and in sight of their prey; see Job 4:10, yea, they shall roar, and lay hold of the prey; seize it with great noise and greediness: and shall carry it away safe; into their own den, the country from whence they come: and none shall deliver it; this shows that respect is had; not to the Babylonish captivity, from whence there was a deliverance in a few years; but the Roman captivity, from thence there is no deliverance as yet to this day.